执勤中队执行任务后，必须（）及时对使用过的装备器材进行一次维护保养。
参考答案：每周
The hospital _________ well, where many wounded ________every day. [ ]
A. is operated; operation
B. operates; are operated on
C. operates; are operated
D. operates; operates on
天然饰面石材中，大理石板材的特点是下列表述中的（）。
A．吸水率大，耐磨性好
B．耐久性好，抗风化性能好
C．吸水率小，耐久性差
D．耐磨性好，抗风化性能差
