________ I can see, there is only one possible way to keep away from the danger.

[　　]

It ________ long before we ________ the result of the experiment.

[　　]

A．will not be; will know

B．is; will know

C．will not be; know

D．is; know

When ________, the museum will be open to the public next year.

[　　]

Not until the early years of the 19th century ________ what heat is.

[　　]

It was the first time that he ________ Beijing.

[　　]

While he ________ in space, Yang Liwei ________ to two astronauts aboard the International Space Station.

[　　]

A．travelled; spoke

B．was travelling; spoke

C．travelled; was speaking

D．was travelling; was speaking

--Do you know the school at all?

--No, this is the first time I ________ here.

[　　]

I will never know what was on his mind at the time, nor will ________.

[　　]

________, when he was already ________ he started to learn painting.

[　　]

A．In the 1980; thirties

B．In the 1980s; in his thirties

C．In the 1900; in thirties

D．In 1900s; in the thirties.

In my opinion, what she said is reasonable ________.

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