题目

You’re sitting in the car, stuck(无法离开的) in traffic. You’re going to be late for school! If only the car could lift(升起) up and fly all the way to the school gate. Well, now you can realize(实现) your wish .     Engineers from the UK built a flying car, called the SkyRunner. This special vehicle(车辆) can reach 185km per hour on the road as a normal(正常的) car, and then fly in the sky at 90km per hour. As the car takes off the ground, a parachute (降落伞) at the back shoots(发射) up and begins lifting the car. Now you’re ready to fly! It lets you fly as high 关于自由落体运动，下列说法中正确的是      A．自由落体运动就是物体沿竖直方向下落的运动    B．自由落体运动是物体只有重力作用下从静止开始下落的运动    C．自由落体运动只有在没有空气的空间里才能发生    D．在有空气阻力时，只要空气阻力不变，物体仍可做自由落体运动