答案：A

题目分析：that引导一个定语从句，先行词为foreigners，故从句的谓语动词应用复数形式，而主句的主语是The number of foreigners ，、“the number +复数名词”作主语时，谓语用单数。故选A。

点评：主谓一致主要遵循的三个原则：语法一致，意义一致，就近原则。主谓一致重点在熟记一些规则。即学即练: The number of people invited _____fifty， but a number of them _____absent for different reasons.

A. were; was  B. was; was　C. was; were  D. were; were

选C