There are some dangerous fish in the river, and I've warned Jack _____ here. [ ]

A. not to swim

B. to not swim

C. swim not to

D. to swim not to

党的各级委员会实行（）。

A、集中领导和分工负责相结合的制度

B、集体领导和个人分工负责相结合的制度

C、集体领导和分工负责相结合的制度