Do you know the little boy ________ is helping the old man cross the road?.
| A．which | B．who | C．whom | D．whose |
I got a letter this afternoon. It was ____ my foreign friend.
| A．from | B．in | C．in | D．at |
I’m all ____ sea and I’ve no idea how to fix my pencil box.
| A．in | B．on | C．at | D．off |
We built this factory ______ top speed and minimum(最少的) cost.
| A．in | B．at | C．with | D．on |
There is a big and beautiful lake ______ the foot of the hill.
| A．at | B．in | C．with | D．on |
We go _____ duty at 8 a.m.
| A．on | B．in | C．at | D．for |