【单选题】It should be apparent that little or nothing is gained by opening a drain at the same time as or after admitting steamThe above sentence probably means _____.
A.
There is apparent condensate in piping
B.
The steam is not discovered after admitting steam
C.
The condensate should be fully loaded in the piping as admitting steam
D.
The condensate should be fully drained from the piping while admitting steam