An A4 sized panel ( 太阳能板 ) put onto the back of a jacket costs __________ US$15. It could __________ a cellphone during a summer walk.
由几个承包商共同承揽某一个工程项目，各承包商分别负责工程项目的某一部分，他们共同对业主负责的一种承包形式是______
对外贸易体制改革的次序，国际上一般认为，第一步是()
One way to understand thousands of new words is to gain __________ good knowledge of basic word formation.
Mr. Smith is in good health now for it is quite a long time since he __________.
