Private cars really provide much convenience to people and they cause too many problems.

问题补充：

Private cars really provide much convenience to people, and they cause too many problems.

A. meanwhile

B. therefore

C. otherwise

D. instead

答案：

(答案→)A. meanwhile

B. therefore

C. otherwise

D. instead

解析：meanwhile同时，期间；therefore因此，所以；otherwise否则，另外；instead反而，代替。句意：私人汽车真的给人们提供了许多方便，同时它们也引起了许多问题。结合语境可知选Ａ。