During prolonged astern maneuvering of the relative expansion between any of the turbine its casing is likely to increase for an alarming level you should (multi choice)

A) Inform the bridge that no further manoeuvring is possible as the turbine are likely to be damaged
B) Reduce the vacuum further to control the relative expansion
C) Keep manoeuvring irrespective of damage to the turbines
D) Request the bridge to try to reduce number of astern movements