21 ．Oranges are usually sold by ____weight, and eggs are sometimes sold by ___ dozen.
A．the; the B．/; the C．/; a D．the; a
22．The girl cried with a expression on her face．
A．frightened B．frightening C．frighten D．frightens
23．Do you think regular exercise ___ good health?
A．benefit from B．reach for
C．make for D．go for
