mechanics

Option A is wrong because velocity has both magnitude and direction. Surely the directions of travel for A and C are changing along their paths, hence they are not of constant velocity.
Option B is wrong because average velocity = displacement/time.
The three girls should have the same displacement over the same time interval, thus having the same average velocity.
Option C is correct because the path travelled by Girl A is the longest, her speed should be the highest in order to complete the journey within the same time interval as the other girls did, but with shorter paths. The acceleration of Girl A thus must be the highest. If not, then girl A wouldn't attain the highest speed among the three girls.

係Boy 定 Girl 呀．．．