( )21.—_____ does he meet his friends?
—_____ a month.
A.How often; Twice B.How long; Twice
C.When; Two D.What time; Two
( )22.—Where are Jim and Tom? Their mother is looking for them.
—They _____ at the moment.
A.run B.runs C.are running D.running
( )23.History is a useful subject. We can learn _____ the past.
A.of B.about C.from D.at
( )24—Where’s Mike?
—He is working _____ physics _____ in the classroom.
A.in; problem B.out; problem C.in; problems D.on; problems
