A substation has zone ground fault protection. Which statement is true?

a. The main will trip before the feeder breakers
b. The feeder breakers send a block to the main and tie so they donít trip
c. The feeder breakers send a block the main and tie so they donít trip until their designated tripping time.
d. The main will trip and block tripping to the other side of the bus

It is my understanding that when zone interlocking is not defeated the breaker will trip at its minimum time no matter what. Defateating zone interlock will allow the breaker to trip at its programmed time delay. My answer would be "C". Can someone help verify this answer?