如图所示,ΔABC中,∠BAC=90°,AD⊥BC于D,若AB=3,BC=5,则AD的长度是( )
A:85
B:45
C:125
D:225
袋装饼干的包装中,常装有一包干燥剂,该干燥剂的主要成分是( )
work on, talk about, be ready for, make a joke, have a rest