1. It’s the most important thing _______ should be done at once.
A. B. that C. which D. who
2. The boy ____ name is Li Lei is my friend.
A. who B. whom C. that D. whose
3. The watch is _____ tells the time.
A. that which B. that C. which D. which that
4. The house ______ we live is very comfortable.
A. that B. which C. in that D. in which
