is known to all,good friends happiness and value to life.
A. It; add
B. As; add
C. It; add up
D. As; add to
网友回答
A. It; add
(答案→)B. As; add
C. It; add up
D. As; add to
解析: as引导的定语从句修饰整个主句; add to sth.使增加,使增强; add sth to sth. 把……加到……里边; add up to总计是……。因句中已有介词to,所以只能选B。