【单选题】What can be inferred from this conversation?
A.
Mary's parents visit Mary regularly.
B.
Mary's children have all worked.
C.
Mary's children are all studying in school.
D.
Mary doesn't visit her parents often enough.
【简答题】硅砂的热膨胀率大,这种特性常易使铸件发生( )缺陷。
【简答题】经济效益评价方法分为静态评价法、动态评价法及 三类。
【单选题】在控制系统中,( )是顺序控制和时间控制的核心:
【单选题】千分尺是一种精度较高的量具,由尺架、测微螺杆、测力装置等部分组成,其测量范围为().
【单选题】Mary ____ from Cuba.