一些英语语法问题,

It is such decisions that have helped give America's communications industries their commercial vibrancy; and that vibrancy,in turn,which explains the cultural voice - power of the United States. 
这里的help 后面怎么能接give呢,有help do sth这种用法吗?


it is apparent that discrimination in jobs,housing and an unnumbered variety of human encounters continues to be rife,and requires undeviating political attention. 
这里的an unnumbered variety of human encounters continues,是an后面省略了主语,unnumbered和variety of human encounters是一起修饰主语吗,可不是a varity of是固定搭配吗,那a 又去哪里了呢?