Select the correct sentence.

Explanation of all the options:

1.His speech is very allusive to be understood

• Explanation: The phrase "very allusive" does not work well with "to be understood." Instead, it suggests a degree of difficulty in understanding, but "very" is not the correct modifier in this context. The structure is awkward and incorrect.
• Incorrect ❌

2.His speech is too allusive to be understood

• Explanation: This sentence correctly uses "too" to indicate that his speech has an excessive level of allusion, making it difficult to understand. This is a grammatically correct and clear construction.
• Correct ✅

3.His speech is allusive enough to be understood

• Explanation: This sentence implies that the level of allusion in his speech is just sufficient for understanding. While grammatically correct, it conveys a different meaning than intended in the context of difficulty in understanding.
• Incorrect ❌

4.His speech is too allusive to understood

• Explanation: This sentence is incorrect because it omits the infinitive "be" before "understood." The correct structure should be "too allusive to be understood."
• Incorrect ❌