21. Expert think that ________ recently discovered painting may be _____ Picasso.
A. the ; / B. a; the C. the; the D. the; a
22. To keep healthy, she ______ cycling as a regular form of exercise after he retired.
A. took up B. caught on C. carried on D. made for
23. —I’ve got to go now.
— Must you? I _________ you could stay for dinner with us.
A. think B. have thought C. thought D. am thinking
