A beam of light will not bend round corners unless ________ (make) to do so with the help of a reflecting device
Matter is the name ________ (give) to everything which has weight and occupies space.
如果队员意外地将球投入该队的本方球篮,对方得分有效()
he teacher told them since light ________ (travel) faster than sound,lightning ________ (appear) to go before thunder.