Institution: AGRANI BANK LTD Exam: Agrani bank Ltd - Officer 04.07.2008
Topic: Fill in the Blank, Subject: English Grammar (ইংরেজি গ্রামার)

Best Answer Explained in Below-:

In the context of scheduling and meeting times, the preposition "at" is the most appropriate choice when referring to a specific point in time. When we say "Let's meet at six o'clock," we are pinpointing an exact time for the meeting. This usage is consistent with standard English conventions for discussing time.

To further clarify, let’s look at the other options:

- **In** is typically used for periods of time (e.g., "in the morning," "in 2023") and does not convey specific timings.

- **For** implies duration or purpose (e.g., "for an hour," "for dinner") and is not used to indicate a specific moment in time.

- **On** is used for days and dates (e.g., "on Monday," "on July 4th"), but not for precise times.

Therefore, "at" is the correct preposition here, as it directly links to an exact time without ambiguity. Using "at" shows that the meeting will occur at a specific moment, making it clear and precise for all parties involved.