As there is less coal and oil, scientists are exploring new ways of making use of _____ energy, such as sunlight, wind, and water for power and fuel.
A.primary | B.alternative | C.instant | D.unique |
Earth is believed ______ by an object the size of Mars at some point in the distant past
before its surface cooled.
A.to be hit | B.to have hit | C.to have been hit | D.to hit |
With temperature ______ so rapidly, we could not go with the experiment.
A.fall | B.falling | C.fallen | D.to fall |
--- Is John in the office?
---I didn’t see ______ there.
A.anyone | B.someone | C.everyone | D.each one |
Because of ______high demand for Type AB blood,____supplies of it are usually limited.
A.the;the | B.不填;不填 | C.不填;the | D.a;the |
His parents never approve of_____ he plans to do, which always annoys him.
A.whatever | B.no matter what | C.no matter when | D.whenever |