．—Let’s back up. Where was I?

—______.

A．You were in the kitchen.

B．You left your book at home.

C．You were having a rest.

D．You were talking about the cause.

房地产市场不是完全竞争的，主要是因为房地产具有()的特性。

A.独一无二 

B.价值最大 

C.寿命长久 

D.易受限制