21. It comes as ______ surprise that ______ dream of space travel will soon come true.
A. a; the B. the; the C. the; a D. a; 不填
22．Stop the child ____he will be falling over．
A．and B．but C．or D．for
23. The girl sitting by the window is the only one of the students who _______ from the countryside in our class.
A. was B. were C. is D. are
