It is possible to perform a continuity test on a 3 phase motor, although it is slightly more labor intensive than for a single-phase motor. For the 3 phase motor a person needs to check both the phase to ground and each phase to phase aspect using a continuity tester, a multimeter or a megger.
Performing a continuity test on a 3 phase motor has 3 steps:
Each phase winding should be the same length, meaning that there should be limited discrepancy between the measurements of each phase. They should all be in the high Megaohm range with only approximately 5 percent difference. If there is significant change between any of the phases, then there is an issue with the wiring of the motor that needs to be addressed before it is used.
This seems like a question from an electrical course, and is probably best answered by referring to your course materials. It's your test question, not ours, and there won't always
90kW = roughly 150A, depending on installation methodology and distance from source, I would start at a 50mm² with a 25mm² IEW or BCEW.