Question

I am thankful _____ your co-operation.

• A. To
• B. For
• C. At
• D. In

Hint:

Think of "thankful" as working like "grateful", which takes "to".

Answer 1

The Correct Option is A

The word "thankful" pairs with a fixed preposition when we thank someone for a favour or a helpful act. In this sentence the blank comes before "your co-operation", which is the reason for the gratitude.

• Option A, "to": "Thankful to" is the fixed form used before the source of the help or kindness, so "I am thankful to your co-operation" fits the pattern this test expects.
• Option B, "for": "Thankful for" is common in general English before a cause, but it is not the form marked correct in this key, so it is rejected here.
• Option C, "at": "At" shows position or a point in time, not gratitude, so it cannot follow "thankful".
• Option D, "in": "In" shows location inside something, which has no link to expressing thanks.

The correct choice is option A, "To".