C
试题分析：注意句子结构，在空前是一个逗号，空前后都是简单句，所以我们需要一个并列连词，然后根据句意可以看出两个句子之间没有转折与选择关系，故选C。
考点：考察并列句
点评：对于并列句的考察一定要注意句子结构还有标点符号的作用。
即学即练：He always thinks highly of himself and _____ makes others unhappy.
A. it B. which C. that D. one 答案：A
对比: He always thinks highly of himself, _____ makes others unhappy.
A. it B. which C. that D. one 答案：B
