Institution: SONALI BANK LTD Exam: Sonali Bank Ltd - Sub-Assistant Engineer (Electrical) - 30.09.2016 ||
Topic: Preposition, Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

The correct answer is "A) on," as the phrase "prides herself on" is the standard idiomatic expression in English. When someone takes pride in something, it means they feel satisfaction or pleasure regarding a particular quality, achievement, or characteristic. In this context, "her beauty" is being highlighted as a characteristic that she feels proud of.

The preposition "on" is used here to denote the source of her pride, indicating that her beauty is the attribute she values and holds in high regard. This specific construction is essential because it illustrates that the pride is derived from her beauty.

In contrast, the other options do not fit correctly in this context. "To" implies direction or purpose but does not convey pride. "Of" suggests possession, which does not communicate the same meaning as "pride." Lastly, "from" could be confusing as it generally indicates a source but does not pair correctly with the verb "pride" in standard usage. Therefore, "on" is the only appropriate choice, making "A) on" the correct answer.