题目内容
Many insects are useful to humans. For example, some farmers put ladybugs on their plants ________ these insects eat insects that destroy crops.
[ ]
A.though
B.because
C.but
D.while
答案:B
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题目内容
Many insects are useful to humans. For example, some farmers put ladybugs on their plants ________ these insects eat insects that destroy crops.
[ ]