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單項(xiàng)選擇題

One cannot learn a foreign language well（）he studies hard.

A.unless
B.if
C.as
D.when

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One and a half hour（）since we arrive. No one has come to meet us.

A.have passed
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On my left（）a wide river; on my right, a dark forest.

A.has been
B.was
C.are
D.would be