21. I would have called her last night, but ____ was a great pity that I forgot her telephone number.
A.there B.it C. this D. which
22. There’s a _____ in our office that when it’s somebody’s birthday, they bring in a cake for us all to share.
A. relationship B. balance C. concern D. tradition
23.How to make wide use of natural energy is the problem still _____ discussion publicly in the newspaper.
A. under ¡¡¡¡ B. on ¡¡¡¡ C. at ¡¡¡¡ D. with
24._____ they are most interested in is ______they can produce more and better cars.
A.That; how B.What; how C.What; what D.That; that