a number of后面接復(fù)數(shù)還是單數(shù)

　　The new management intends to institute a number of changes.

　　新任管理層打算實(shí)行一些改革。

　　There are a number of different points of view on this issue.

　　在這個(gè)問題上意見紛紜。

　　I have a number of things to do today.

　　我今天有許多事情要做。

　　A number of measures were taken to alleviate the problem.

　　采取了一系列措施緩解這個(gè)問題。

　　A number of social factors influence life expectancy.

　　諸多社會(huì)因素左右著人的預(yù)期壽命。