题目内容：

How many cities has the Smiths traveled to since they came to China last week?
A.have,traveled B.was,traveled
C.did,travel to D.has,traveled to

优质解答

有since存在,所以是"完成时" has/have travelled
the Smiths 指的是Smith一家,作为一个整体,所以是has travelled
自从上周他们去中国之前,Smith一家已经去过多少个国家?