1.请问a variety of 等于varieties of 吗？

课文中的you can buy varieties of Chinese tea这里可以替换为a variety of Chinese tea吗？如果不可以的话，有可以替换的情况吗？

2.请问a variety of 和varieties of都可以接不可数名词吗？

a variety of/varieties of food/music这里的food和music需要用复数形式吗？

3.词典说a variety of+名词时谓语动词要用复数形式，是否说明谓语动词的数由名词决定？那如果接的是不可数名词呢？

下列句子be动词使用正确与否：

A variety of food is sold here.

A variety of foods are sold here.

Varieties of food is sold here.

Varieties of food are sold here.

4.也是课文出现的：diverse culture of the USA 请问为什么这里culture不用复数？