There was a consideratable variety of a pinions.谓语动词为什么不用复数?

There was a consideratable variety of a pinions.谓语动词为什么不用复数?
我从语法书中看到的这句：
There was a consideratable variety of a pinions.
1.为什么这句中的谓语动词要用单数形式?
2.在这句中的"variety"是不可数名词吗?
There were a lot of people at the meeting yesterday.
3.而这句中的"lot"也是不可数名词吗,上句的谓语动词为什么没有和这句的形式一样?
对不起 原句是
There was a considerable variety of opinions.
回复2楼 怎么看出来的 这句的主体名词是 variety 而不是opinions呢？
而且如果variety在这里做品种，种类讲的话应当是可数名词，它接在considerable之后为什么又不是复数呢
例如这句：There are different varieties of plants in the garden.