At 13 Samuel received a training course in drawing for three years he got a good opportun

问题补充：

At 13，Samuel received a training course in drawing for three years， he got a good opportunity for further development.

A. after that

B. after which

C. after it

D. after this

答案：

A. after that

B. after which

C. after it

D. after this

解析：B

解析after which意为“after he received a training course in drawing for three years”。句中没有并列连词，故不能选C、D两项；that不能引导非限制性定语从句，故A错。