题目内容：
A on
B for
C at
D by
参考答案：
答案解析：
单选题：A on B for C atD by
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A on
B for
C at
D by
A on
B for
C at
D by
根据材料，回答题：A. Natural sponges become cleaning aids.B. We pollu
根据材料，回答题：A. Natural sponges become cleaning aids.B. We pollute the ocean when we
请在第（53）处填上最佳答案。
请在第（53）处填上最佳答案。
回答第65空。
回答第65空。A．A missing B．B grown C．C big D．D fresh
回答第56空。
回答第56空。A．A fall B．B flow C．C roll D．D gather
Besides the backdrop of bad employment news and a cooling ec
Besides the backdrop of bad employment news and a cooling economy， which of the