Institution: বরিশাল বিশ্ববিদ্যালয় Exam: খ ইউনিট || বরিশাল বিশ্ববিদ্যালয় || 2014
Topic: Sentence (বাক্য), Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The sentence "I was terribly disappointed with my grade because I was ............ very hard." requires a past perfect tense to properly convey the sequence of events and the speaker's feelings. The correct answer is D) "had studied."

Using "had studied" indicates that the studying occurred before the disappointment about the grade. In this context, "had studied" (past perfect) highlights that the speaker had put in significant effort leading up to the point of receiving the grade. This emphasis is crucial because it illustrates that the level of effort expected to yield a different outcome (a better grade) was not met, leading to disappointment.

The other options do not appropriately express this sequence of events:

- A) "studied" is incorrect because it would imply a simple past action without context.
- B) "study" is not appropriate since the sentence requires a past form to match "was."
- C) "was studying" suggests an ongoing action but fails to indicate that the studying was completed before receiving the grade.

In summary, "I had studied" is the best choice because it effectively communicates the prior effort and the unexpected result, aligning with the speaker's disappointment.