Drop in 顺便拜访 如
Do drop in if you happen to be passing!
如果你碰巧经过时进来坐坐.
Drop out 离开,退出 如
He says he has dropped out,and won't attend college any more.
他说他退了学,以后也不会去上大学了.
Pick out 取出,去掉 如
The child refuses to eat this fruit without first picking out the stones.不把果核取出来,那个小孩就不会吃这水果.
pick up 安排接取
题中是说cooking class 改到了星期二,所以我要退出,以便于去接送我的女儿
选C