Wash your hands＿＿＿you have dinner.A.before B.but C.when D.so
还有几题：Early men found fire very＿＿＿millions of years ago.
A.use B.useful C.useless D.uses
Only a quarter of the Earth is＿＿＿.
A.oceans B.land C.forests D.seas