用正确的介词或副词填空：
问题描述：
用正确的介词或副词填空：
1.He received a letter _______my sister.
2.A number _______people are in the room.
3.He asked his father______some money.
4.I call _________my mother every week.
最好能为我讲讲填这些词的原因,thank you!
答
1.from——receive a letter from sb——收到某人的来信
2.of——a number of——许多,大量
3.for——ask for——需要、请求,要求
4.up——call up——（给某人）打电话