分类：教育/科学-学习帮助
问题：必修一__isknowntousall,goodfriends_ 
__is known to us all,good friends__happiness and value to life.A.It;addB.As;add.It;add toD.As;add to
回答：__is known to us all,good friends__happiness and value to life. 
A.It;add 
B.As;add 
C.It;add to 
D.As;add to

你仔细看句子，后面已经有to了，value （to） life. 
如果你再选add to，不是重复了？