______ his pocket money, Bill bought many books for the poor children.
A：Use
B：In
C：With
D：Pay
go, you, with, did, who (?) （连词成句）
____
某同学进入泳池前以为池水很浅，踩下去后却有一种“踏空”的感觉，则水的实际深度要比看上去的深一些，其原因是（ ）
