[单选题]
Ball A is dropped from the top of a builjhd+;gcmu9;x 5ba f k4ding. One second later, ball B is drop asvrf+c, :q+ hccr.3 okdk,9aped from the same building. As time progresses, the difference in their speedsaqc3k.d ,+ +rorcs 9vk:afc,h
A. increases.
B. remains constant.
C. decreases.
D. cannot be determined from the information given.
