Piston No2 of main engine has been removed, and it will be （） by noon tomorrow.

A.a low load on that cylinder
B.sluggish piston ring action
C.excessive piston crown cooling
D.excessive clearance of piston pin

A.the same as
B.similar to
C.separated from
D.different from

A.safety valve
B.indicator cock
C.blow-down valve
D.start valve