一炮弹由于特殊原因在水平飞行过程中,突然炸裂成两块,其中一块作自由下落,则另一块着地点(飞行过程中阻力不计):[ A ]
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
免费的网站请分享给朋友吧