等差数列{an}共有2m项，其中奇数项之和为90，偶数项之和为72，且a2m-a_爱下问搜题

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问题选择题

等差数列{a_n}共有2m项，其中奇数项之和为90，偶数项之和为72，且a_2m-a₁=-33，则该数列的公差为[ ]

A．-1

B．-2

C．-3

D．3

答案

答案：C

选择题

When they awoke the next morning, they were surprised to find a ___ of fog floating in the air. [ ]

A. cover

B. blanket

C. piece

D. mixture

问答题简答题

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