As you say, a strangely worded set of answers. As before, I note that you only quote 3 answers. The current UK CAA exam papers all feature 4 answers (ever since they stopped negative marking for wrong answers and changed the pass mark from 70% to 75%)
As far as I am concerned, the answers you quote aren't using current terminology for the instruments. Generally, the Earth gyro is referred to as the Attitude Indicator or AI, the space gyro is the Direction Indicator or DI. Traditionally, both these two are powered by the vacuum pump, a hangover from the days when they were powered by venturi systems that sucked. The Turn Coordinator, which invariably includes the slip/skid ball is usually an electrically powered gyro, to provide a different source of power should the vacuum system fail.
Can I respectfully suggest that you look at the latest examination preparation publications, available from popular suppliers of pilot equipment?
TOO