Choose the sentence with the correct preposition:-

The correct answer is Option (1) → I have not met Rita since last year.

Since and for with the present perfect:

• Since is used with a point of time at which an action or state began (since Monday, since 2010, since last year).
• For is used with a period of time (for two days, for a year).
• This sentence: "last year" is a point of time, so the sentence needs since.
  Example: We have lived in this town since 2015.

Why the Other Options are Incorrect?

Option 2: I have not met Rita for last year. — Incorrect. For needs a period (for a year), not a point of time like "last year".

Option 3: I have not met Rita in last year. — Incorrect. "Last year" takes no preposition when it names a time ("I met her last year"), and "in" does not show a starting point.

Option 4: I have not met Rita to last year. — Incorrect. To marks a destination or end point, not the starting point of a period.