Fill in the blanks:

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

The phrase "weak in" is used to describe a lack of proficiency or skill in a particular subject, area, or activity. It indicates that someone does not perform well or has insufficient knowledge in that specific field.

For example:

• He is weak in Mathematics.
• She is weak in grammar.
• The team is weak in defense.

Other prepositions like "at" can also sometimes be used (e.g., "weak at sports"), but "in" is more commonly and idiomatically correct when referring to academic subjects or general areas of skill.

His allegation was Based on fact.

The correct preposition to fill the blank is "with".

The phrase "familiar with" is used to indicate that someone has knowledge or experience of a particular person, thing, or subject. It implies a state of being acquainted with something or someone.

For example:

    
• "Are you familiar with the new project guidelines?"
    
• "She is familiar with ancient history."

While "familiar to" also exists, its meaning is different. "Familiar to" means that something is known or recognized by someone (e.g., "His face is familiar to me"). In the given sentence, "I am familiar .......... them," the subject "I" possesses the familiarity, therefore, "with" is the appropriate preposition.

The word "besides" is used here as a preposition meaning "in addition to" or "apart from". It indicates that the person knows Bengali in addition to knowing English.

For example:

    
• Besides English, she speaks Spanish fluently.
    
• What other hobbies do you have besides reading?

In this context, "besides" emphasizes the inclusion of Bengali as an additional language known, alongside English. Other grammatically correct options could be "and" or "as well as," but "besides" specifically highlights the additive nature of the knowledge.

by

In English grammar, the preposition "by" is frequently used to indicate the extent or degree of a difference, especially when comparing quantities, measures, or age. It specifies the margin or amount by which one thing differs from another.

• Expressing Age Difference: When stating how much older or younger someone is, "by" is the correct preposition. For example, "He is older than I by five years" clearly specifies that the age difference is exactly five years.
• Other Differences: This usage also applies to other contexts, such as "The stock price rose by 3%" or "She is taller than her sister by an inch."
• Contextual Application: In the given sentence, "He is older than I ______ five years," the blank requires a word that conveys the precise measure of the age difference. "By" serves this purpose accurately, indicating the margin of comparison.