My father didn’t go to bed ______ he washed his car last night.
A. until B. after C. when D. since
We can’t do two things _____.
A. all the time B. on time C. at times D. at a time
Jim’s shirt is made _____ silk , and it’s made ______ china.
A. in, of B. from, of C. of , in D. from , in
No smoking, please. It’s ____ the rules.
A. against B. for C, on D. at
Although we are young, ______ we can still do something to help them.
A. but B. / C. and D. however
It is necessary _____ something to protect our environment.
A. do B. to do C. does D. doing
