1. Some of+名词

当主语是“ all of/ some of/ none of/ half of/ most of+名词”时，谓语由名词决定。

Most of the money is given by my mother. 大部分钱是妈妈给的。

Most of the students in this class are boys. 这个班大多数学生是男孩。

2. Plenty of+名词

当主语是“ lots of/ plenty of/ loads of+名词”时，谓语由名词决定。

Lots of food here is delicious. 这儿很多事物都很好吃。

Lots of people here like dancing. 这儿很多人都喜欢跳舞。

3. A portion of+名词

当主语是“ a portion of/ a series of/ a pile of+名词”时，谓语用单数。

A large portion of the students is from China. 这儿学生中很大一部分都来自中国。

A large portion of the report is missing. 这份报告很大一部分都丢失了。

4. A kind of+名词

当主语是“ a kind of/ a type of/ a sort of+名词”，由于名词只能是可数名词单数和不可数名词，所以谓语为单数。

There is a kind of rose on the table, which is very expensive.

桌上放着一种玫瑰，价格昂贵。

5. Many a+名词

当主语是“ many a+名词”和“ more than one+名词”，谓语用单数。

Many a girl has toys. 很多女孩都有玩具。

There is more than one map on the wall. 墙上有很多地图。

因此，当主语是表示不确定数量的名词时，谓语动词到底是单还是复，可依据以上规则，一一对号入座。