( )21．I usually go to school on ________ foot． A. a B．the C．／
( )22．一How often do you see your grandparents?
一 ________ . A. Five days B．Once a month C. In a week
( )23．When I came back yesterday evening，my brother ________ his homework
A. is doing B. has done C．was doing
( )24．一When were you born?
—I was born ________ a cold winter morning in 1996． A. on B. in C. at
