下列关于溶液的说法正确的是  (    )

A．溶液都是无色的

B．溶液都是混合物

C．溶液中的溶质都是固体

D．饱和溶液一定是浓溶液

Because of the（）nature of the agreement，I was reluctant to discuss with him in office.

A.confidential

B.delicate

C.secret

D.sophisticated