A was receiving B had received C is received D received A played B found C done D led A those B which C they D who
此处需要用一半过去式,所以只能选D received. 这个考察的是固定搭配的使用,“play a role in”为固定搭配,因此选A played. 首先,考虑从句,因此一定使用which或者who, 然后就要根据内容啦,这里根据内容可以判断这里是指代前文中的galaxy clusters,所以用which, 选B。 这题的判断需要根据文章的内容。在文中“Couch除了做自己的工作之外还进行了一些其他工作。” 所以应该用A in addition to.
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