Stall warning is required to occur:

After the stall

Only during approach

Only during takeoff

Before the stall, providing adequate warning for recovery (typically 5-10 kt above stall speed)

Correct

Explanation

Regulations require natural or artificial stall warning (buffet, stick shaker) to occur with adequate margin before the stall.

Test yourself with random questions from Principles of Flight and all other ATPL subjects.