When a giraffe has ______ drink, it has to stand with its front legs wide apart in order to reach ______ water easily.

A．不填；不填

B．a; the

C．the; 不填

D．不填；the

一物体从45m高处自由下落，在最后1s通过的高度是______s，最后1s的初速度是______m/s，最后1s内的平均速度是______m/s。