有下列情况时，不准装药放炮，爆破地点附近（）米内，矿车、或其_爱下问搜题

搜题请搜索小程序“爱下问搜题”

问题单项选择题

有下列情况时，不准装药放炮，爆破地点附近（）米内，矿车、或其他杂物堵塞巷道1/3以上。

A、10

B、20

C、30

D、40

答案

参考答案：B

单项选择题

设关系R和S具有相同的度，且相应的属性取自同一个域。下列哪一个关系代数运算的结果集合为{t｜t∈R∧t[*]S}？

A．R∪S

B．R-S

C．R×S

D．R∩S

单项选择题

Questions 14-23

·Look at the ten statements for this part.
· You will hear a passage about "Inflation" You will listen to it twice.
·Decide whetheryou think each statement is right(R), wrong(W) or not mentioned(NM).
·Markyour answers on the Answer Sheet.

There have been higher and higher rates of inflation in the US over the years.

A．Right

B．Wrong

C．Not Mentioned