2017-2018
C．or D．because
解析：选D Elva说她不需要加入这样的互助小组是“因为(because)”她有Irma。
Ⅱ.短文改错
Mike is one of my sister's classmate. He is a fulltime chemistry student, though at weekends he worked in the university bookshop. She is a member of the Students' Union, and helps holding a few different events. In his free time, he plays an active part in quite a lot clubs and societies. For example, he belongs in the English Club, helping out with many of the organization work. He is also a strongly supporter of the university basketball team. In fact, he's recently been taken on the role of their minibus driver, and takes them to matches once the week.
答案：第一句：classmate→classmates
第二句：worked→works
第三句：She→He; holding→hold
第四句：lot后加of
第五句：in→to; many→much
第六句：strongly→strong
第七句：去掉been; once后面的the→a
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