– Why did they help Mrs Brown with her work? – Because she was .A. an old friend of themB

问题补充：

– Why did they help Mrs Brown with her work?

– Because she was .

A. an old friend of them

B. the friend of them

C. a the their friend

D. a good friend of theirs

答案：

A. an old friend of them

B. the friend of them

C. a the their friend

(答案→)D. a good friend of theirs

解析：句意：为什么他们帮助布朗夫人做她的工作？因为她是他们的一位朋友。a good friend of theirs=one of their good friends他们的一位好朋友，所以选D。