选 A. to have studied，不定式的完成式（也叫：完成体），说明动作发生在is said 之前，此前已经在国外深造4年了。又如： 

He is said to have moved to Chicago. 

据说他已搬到芝加哥去了。

She is said to have been an actress about twenty years ago. 

据说她在20年以前曾是一位女演员。

Columbus is said to have discovered America in 1492. 

据说哥伦布于1492年发现了美洲。