混凝土的抗冻性是指混凝土在饱和状态下，经多次冻融循环作用而不严重降低强度的性能，其抗压强度下降不超过25%，质量损失不超过（）。

A.3%

B.5%

C.7%

D.9%

Multipurpose Internet Mail Extension (MIME) is a (1) document messaging standard in the Internet enviroment, with MIME, users can send (2) Email messages that include audio, video, graphices, and text to any other user of a TCP/IP network. Richtext information can also be (3) into messages. It defines the fonts, formats, and (4) features of a document so the document can be easily (5) on many different types of systems.

1（）

A．complete

B．compound

C．simple

D．efficient