. 4.两根材料和长度均相同的圆轴,第一根的直径是第二根的两倍,若受相同扭矩的作用,则两根轴的扭转角之比为()。
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