11. 平面四杆机构中,如果最短杆与最长杆的长度之和大于其余两杆的长度之和,最短杆为连杆,这个机构叫做
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