21. He is the person _______ I believe has the ability to do this challenging job.
A. who B. whom C. him D. which
22. --- It’s a good day for a picnic!
---Yes, _____ yesterday
A. So was it B. So it was C. So it is D. So is it
23. In the corner, there is a garbage can arepiecesof garbage and wastepaper.
A. that B. around which C. around that D. which
