31. Just at that time, a strange young man broke into our office, his hands _____ in his pockets.

A．sticking

B．stuck

C．to stick

D．were stuck

小华的爸爸在给移动电话的电池“充电”，在这种情况下，移动电话的电池是______（电源或用电器），在“充电”时，它把______能转化为______能．