1.There is no doubt ________ Catherine is fond of dancing, for she always practices it on weekends.
A. whether B. if C. that D. which
【答案】C。解析：考查同位语从句，句意：毫无疑问Catherine喜欢跳舞，因为她总是在周末练舞。分析句子的结构可知，逗号之后为“for”引导的原因状语从句，逗号之前是主句，主句中结构为"There is no doubt that…"意为"毫无疑问…"，连词"that"引导同位语从句解释说明名词"doubt"的具体内容，同位语从句中句子结构和意思已完整，"that"无意义也不充当成分，只起连接词的作用.故C为正确答案。
2.You have seen the girl ________ sister is a Chinese teacher.
A. whom B. of whom C. whose D. of which
【答案】C。解析：此句先行词为the girl，定语从句为sister is a Chinese teacher，二者构成的完整句为The girl’s sister is a Chinese teacher.先行词的’s所有格构成的所属关系结构在从句中作定语。故选C。
3.He found it increasingly difficult to read, ______ his eyesight was beginning to fail.
A. and B. for C. but D. or
【答案】B。解析：此题考查原因状语从句。“his eyesight was beginning to fail”是“he found it increasingly difficult to read”的原因，因此本题应选用可以表示原因的连词for引导原因状语从句。故选B。