in the past few years

Housing prices ___ sharply in the past few years.

a. dropped

b. have dropped
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1. Which one is more appropriate a or b? Please explain.

2. What does 'in' mean?

3. Can I replace 'in' with 'during' or 'within' and with no meaning change?


Thanks

Housing prices have dropped sharply in the past few years.

Is it correct ?

Why?