Answer:
C. to go ashore.
Step-by-step explanation:
The word "disembark" refers to the act of getting off from a particular place, like getting off from the bus, vehicle, or to get down from a vehicle. This means that disembarking is to leave a vehicle.
In the given context, the sentence reads as "a guide will greet you as you disembark from the boat to tour the city". Here, the verb "disembark" means to get ashore, to leave the boat.
Thus, the correct answer is option C.