To answer this question, you need to understand the concept of a free-hit in T-20 cricket.
A free-hit is awarded to the batsman when the bowler delivers a foot fault no ball. A foot fault no ball occurs when the bowler oversteps the popping crease while delivering the ball. This means that the bowler's front foot lands beyond the line, indicating a no ball.
When a foot fault no ball is called by the umpire, the batsman at the non-striker's end gets a free-hit. This means that the batsman cannot be given out by any means on the next delivery, except for a run-out. The batsman can take a big swing at the ball without worrying about getting out, giving them an advantage.
Therefore, option A is correct. The free-hit comes into play when the bowler bowls a foot fault no ball.