— I have to get to the post office by six o'clock, but it is almost six now.

— _______. This clock is fifteen minutes fast.

[      ]

A. That's too bad

B. Sounds good

C. Sure, you can

D. Take it easy

在成组病例对照研究中，对OR值的描述哪个是正确的

A．O＞1，说明某因素是危险因素

B．OR＜1，说明某因素是危险因素

C．OR＝1，说明某因素是危险因素

D．OR＝1，说明某因素是保护因素

E．以上均不是