21.分数词的主谓一致

“分数或百分数+of+名词”构成的短语及由“a lot of，lots of，plenty of，half of，a heap of，heaps of+名词”构成的短语作主语时，谓语动词的数与短语中of后名词的数保持一致。

A heap of rubbish has been cleaned away．

一堆垃圾已被清除掉。

A great pile of buildings are being built on the banks．

河的两岸正在兴建一大群建筑物。

More than 70 percent of the surface of our planet is covered by water．

我们的星球表面有70%多都被水覆盖着。

One third of the students are girls in our group．

我们队1/3的学生是女生。