58. Engage the turning gear and keep it running for 15 minutes.

A、
A、 Disengage in turning gear to make it run for 15 minutes.;

B、
B、 Put in turning gear and keep it running for 15 minutes. ;

C、
C、 The turning gear is engaged 15 minutes ago.;

D、

D、 The main engine should be stopped for 15 minutes.