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在氧气性质和制取的实验中，需完成碳和铁丝在氧气中燃烧两实验，实验操作： ①利用高锰酸钾制取氧气，他用如下图中的发生装置____； ②制氧时，小明未能收集到两瓶氧气，其可能的原因有_______； A．没有塞紧试管塞 B．试管口放有棉花 C．没有及时更换收集第二瓶 D．加热前已将集气瓶灌满水倒立于水槽中 ③小明采用下图方法收集，从水槽中取出充满氧气的集气瓶，正放于实验桌上，发现瓶口上方的玻璃片容易滑动，其原因是_______________。
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举一反三
【单选题】It's high time we () the lecture because everybody has arrived.
A.
will start
B.
shall start
C.
start
D.
started
【单选题】—The frequent terrible coal mine accidents killed more than 1000 people in China last year. —_______.
A.
That’s the case
B.
Quite OK
C.
Certainly
D.
I agree
【单选题】—The frequent terrible coal mine accidents killed more than 1000 people in China last year . — .
A.
Quite OK
B.
Certainly
C.
That’s the case
D.
I agree
【简答题】The hall _______ (hold)1000 people.
【单选题】It is high time ______ him a severe lecture for being late often.
A.
you give
B.
you gave
C.
you will give
D.
you should give
【单选题】The room is big enough .It _______hold 1000 people. [ ]
A.
may
B.
must
C.
can
D.
have to
【单选题】If the number of people unemployed is 100, the number of people employed is 1000, and the working-age population is 1400, then the labor force is
A.
1000.
B.
1100.
C.
1400.
D.
1500.
【单选题】The meeting ended______his lecture on high education.
A.
up in
B.
by
C.
up with
D.
up
【简答题】发动机电控系统ECU的功能主要有哪些?
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