In the following sentence, the highlighted preposition does not fit. Select the correct word from the options provided to replace the highlighted word.
My grandfather will come here at a week.

Correct option is A

The correct substitution of the highlighted word is (a) within.
Explanation:
The phrase within a week means before one week has passed. (एक सप्ताह के भीतर) The preposition at is incorrect because it is generally used with clock times or specific places, not with a period indicating a deadline.
The corrected sentence is:
My grandfather will come here within a week.
Grammatical Rule Used:
Within + period of time is used to indicate that something will happen before the end of that period.
Example:
· Please submit the assignment within three days.
· She will return within a month.
Why other options are incorrect:
· (b) off: Does not indicate time in this context.
· (c) with: Indicates accompaniment, not time.
· (d) upon: Means "on" or "immediately after," and does not fit this expression.
Information Booster:
Common time prepositions:
· In two days (after two days)
· Within two days (before two days are over)
· By Monday (not later than Monday)
· At 5 o'clock (specific time)