Mark drives his car too fast and what's more very carelessly worries his mother.A. a　　

问题补充：

Mark drives his car too fast and, whats more, very carelessly, worries his mother.

A. a

B. what

C. it

D. which

答案：

A. a

B. what

C. it

(答案→)D. which

解析：答案：D。考查定语从句。此处which引导非限制性定语从句，同时在从句中作主语。