Change the following sentences as directed:

The correct article to fill in the blank is "the".

The definite article "the" is used before a noun when that noun is specific or particular, or when it has already been mentioned or is understood from the context. In the given sentence, "key to success" refers to a specific and well-understood concept – the singular, unique path or factor that leads to success. When we talk about "the key to success," we are not referring to just any key, but the specific, universally recognized key.

Using "a" or "an" (indefinite articles) would imply that there are many keys to success and hard work is just one of them, which might be true in a broader philosophical sense, but the common idiom "the key to success" uses the definite article to emphasize its singular importance or definitive nature.

The preposition "from" is used to indicate origin or source. In the phrase "people from all walks of life," it signifies that individuals originate or come from various social strata, professions, or backgrounds, highlighting the diversity of users.

The preposition "on" is correctly used with "occasion" to denote a specific event or time. "On occasion" is an idiomatic expression meaning 'sometimes' or 'when an event calls for it,' fitting the context of using flowers for particular celebrations or events.

The city's new stadium, built for the Olympics, has become a white elephant due to its exorbitant maintenance costs and lack of public use.

A "white elephant" is an idiom that refers to a possession that is useless or troublesome, especially one that is expensive to maintain or difficult to dispose of. The phrase originates from the historical practice in Southeast Asian kingdoms, particularly Thailand, where white elephants were considered sacred animals. These animals were revered and could not be put to work, making them extremely expensive to house and feed. Kings would sometimes gift a white elephant to a courtier they wished to financially ruin, as the cost of caring for the sacred animal would be a significant burden.

To change an active voice sentence into a passive voice sentence, the object of the active sentence becomes the subject of the passive sentence. The verb is transformed into a 'to be' verb (am/is/are/was/were) followed by the past participle (V3) of the main verb. The original subject of the active sentence, if included, appears after 'by'.

In the given sentence, "The Chinese" is the subject, "put" is the verb, and "a lot of emphasis on unity" is the object. Since "put" is in the simple present tense, the 'to be' verb used in the passive voice will be "is" (as "a lot of emphasis" is considered singular). The past participle of "put" is also "put". Therefore, the passive form is "A lot of emphasis is put on unity by the Chinese."

The correct article to fill in the blank is 'a'.

This is because even though the word "unique" starts with a vowel 'u', its initial sound is a consonant sound, specifically the 'y' sound as in 'you' (/juːniːk/). In English grammar, the choice between 'a' and 'an' depends on the sound of the word immediately following the article, not necessarily the letter it starts with.

Rule: Use 'a' before words that start with a consonant sound. Use 'an' before words that start with a vowel sound.

• Examples for 'a': a university (starts with a 'y' sound), a European (starts with a 'y' sound), a one-way street (starts with a 'w' sound), a book, a cat.
• Examples for 'an': an apple, an hour (the 'h' is silent, so it starts with a vowel sound), an umbrella.

It is high time we changed our bad habits.

The phrase "It is high time" (or sometimes "It's about time") is used to express that something should be done immediately or that it is already overdue. This construction is a common fixed expression in English grammar.

Grammatically, when "It is high time" is followed by a subject, the verb that follows must be in the simple past tense, even though the meaning refers to the present or future and implies a sense of urgency or that an action is overdue. This structure uses the subjunctive mood, indicating a hypothetical or desired situation rather than a factual statement. For example, "It is high time you found a job" means you should find a job now, implying you should have done it earlier.

Alternatively, the phrase can also be followed by an infinitive with 'to' ("It is high time to + verb"), in which case it refers to the general situation and does not specify who should perform the action. For example, "It is high time to address climate change."

The word "myself" is a reflexive pronoun. Reflexive pronouns are used when the subject of a sentence is both the doer and the receiver of the action. In this sentence, the subject is "I", and the action of "not to hurt" is directed back to "I". Therefore, "myself" correctly reflects the action back to the subject.

Reflexive pronouns include: myself, yourself, himself, herself, itself, ourselves, yourselves, and themselves. They must always agree in number and gender with the subject they refer to.

Direct speech is a way of reporting what someone has said by repeating their exact words, enclosed within quotation marks. It preserves the original tense and pronouns used by the speaker. The reporting clause (e.g., "He says") is typically separated from the quoted words by a comma.

The given sentence, "He says, 'I am ill'," is already presented in direct speech form. The speaker's exact words, "I am ill," are enclosed in quotation marks, and the reporting verb "says" introduces them. Therefore, no transformation is required to make it direct; it already is.

She said, "I have completed the task."

To convert this sentence from indirect speech to direct speech, several rules must be applied:

    
• The reporting verb 'said' remains as it is.
    
• The conjunction 'that' is removed.
    
• The reported clause, which was in Past Perfect Tense ('she had completed'), reverts to its original tense in direct speech. In this case, 'had completed' typically originates from 'have completed' (Present Perfect Tense) or 'completed' (Simple Past Tense) in direct speech. 'I have completed the task' is a common and appropriate transformation here.
    
• The pronoun 'she' changes to 'I' because the original speaker is directly quoting themselves.
    
• Quotation marks (" ") are used to enclose the exact words spoken, and a comma is used to separate the reporting clause from the direct speech.

The given sentence uses the grammatical structure 'too...to...'. This construction is used to express that something is in excess of what is desirable or possible, leading to a negative outcome or inability to perform an action. The general pattern is:

    
• Subject + verb + too + adjective/adverb + (for + object/noun) + to + base form of verb.

In the sentence, "The poem is too difficult for the students to understand," 'too difficult' indicates the excessive nature of the difficulty, and 'to understand' specifies the action that becomes impossible or very challenging due to that excessive difficulty. This structure implies a negative sense, meaning the students cannot understand the poem because it is excessively difficult.

Another common way to express a similar idea is using the 'so...that...not' structure. For example, the given sentence could be rewritten as: "The poem is so difficult that the students cannot understand it."