Because airplanes are intended to have long lives, their flight safety must be assured.
因为飞机是要有很长的寿命，所以必须保证飞行安全
A.Since airplanes usually have long service lives, their flights are surely safe. B.It is mandatory to ensure the flight safety because of the long lives of airplanes C.Despite the long lives of airplanes, their flight safety cannot be assured正确答案B
