单选题＿＿＿＿＿＿＿＿＿ work has been done to improve the peopleˊs living standard. 的答案

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题目内容：
＿＿＿＿＿＿＿＿＿ work has been done to improve the peopleˊs living standard.
题目选项

A great deal of

A large number of