Man: The front tire is flat, and the seat needs to be raised.
Woman: Why not take it to Mr. Smith
Question: What kind of work does Mr. Smith probably do

A．He fixes bicycles.

B．He raises sleep.

C．He sells chairs.

D．He's a gardener.

对并发操作若不加以控制，可能会带来（ ）。

A．不安全

B．死锁

C．死机

D．不一致