31. Some institutions have established reading clubs to promote reading but the effort, though ________, is far from enough.
A. appreciated      B. appreciating       C. having appreciated D. to appreciate
31. 【答案】A
【解析】考查非谓语动词的用法。过去分词短语作状语。一些机构已经建立了阅读俱乐部来促进阅读，但这种努力虽然受到赞赏，但还远远不够。