21. The biggest whale is ___ blue whale, which grows to be about 29 meters long—the height of ____ 9-story building.

A. the; the           B. a; a               C. a; the             D. the; a

22. Encourage your children to try new things, but try not to        them too hard.

A. draw                     B. strike             C. rush                        D. push

23. At the age of 29, Dave was a worker,        in a small apartment near Boston and ______ what to do about his future.

A. living; wondering                                  B. lived; wondering

C. lived; wondered                                  D. living; wondered