压边浇口的压边宽度一般为（）。

A.2～7mm

B.7～10mm

C.10～15mm

D.20mm以上

Foam is a very effective smothering agent and（）.

A.it provides cooling as a secondary effect

B.works well on extinguishing electrical fires

C.can be used to combat combustible metal fires

D.All of the above