用括号内所给动词的适当形式填空。
小题1:Recently I listened a song ____ Heart Strings.(call)
小题2:The telephone (invent) before the car.
小题3:The workers in the factory is made ______________ (work) 16 hours every day.
小题4:He said he ____________(be) a scientist some day.
小题5:Keep clean please. It is ____________(correct) to litter there.