The function of the bypass valve on the self-contained breathing apparatus is to（）.

A.control the pressure of the oxygen as it enters the body

B.allow the wearer to manually give himself oxygen

C.release excess heat which would otherwise cause the bottle to explode

D.allow exhaled gases to pass outside the bottle

以下哪些是电缆的敷设方式（）

A.管道

B.沟槽

C.直埋

D.架空