___to be checked and refuelled. ( ) A: All the aircrafts has B: All the aircrafts have C: All the aircraft has D: All aircraft must

What is the meaning of "aviation" ? A: transportation B: vehicles C: communication D: the flying of aircrafts

At the turn of the twentieth century, ________ dominated land transport. A: railways B: aircrafts C: ships D: tanks

On the future battlefield, laser technology will be used ______. A: in the communication between vehicles and aircrafts only B: to both sending information to and receiving information from satellites C: widely in war due to its high capacity and low weight D: exclusively to handle the transmission of voice messages

Which of the items are exempted from environmental protection tax? A: Taxable pollutants discharged by large-scale farms B: Taxable pollutants discharged by mobile pollution sources such as boats and aircrafts C: Sewage discharged directly to the environment by a school D: Solid waste comprehensively utilized by taxpayers that conforms to the national and local environmental protection standards