It is you that … to write the letter

Analyze the question

The sentence is a cleft construction ("It is you that ..."). We need the correct verb form after "that", and we must also check whether "suppose" or "supposed" is right.

Explain the concept

1. Agreement in cleft sentences: In "It is you that ...", the relative pronoun "that" refers back to "you". So the verb after "that" agrees with "you" (second person), not with "it". This means we use are, not "is".
2. Supposed to: The expression meaning "expected to" or "obliged to" is "be supposed to". It must be the past participle supposed, not "suppose".

Step-by-step solution

• Antecedent of "that" is "you", so the verb is are. This eliminates A and B.
• "Are suppose" (C) is wrong because the participle must be "supposed".
• "Are supposed" (D) is correct: "It is you that are supposed to write the letter."

Answer: D. are supposed

Tip: In "It is I/you/we/they that ...", make the verb after "that" agree with the person right after "is". For example: "It is I who am here" and "It is you who are late". Also remember that "supposed to" always ends in -d.