Relative dating is used to determine the

a) actual date of an event
b) length of time between events.
c) age of one event in comparison with other events.
d) rate at which a geologic process occurs.

c) age of one event in comparison with another

Explanation:

The relative dating is a commonly used method among the geologists, paleontologists, and archaeologist. This method is used for determining the order of events that happened in the past, or rather the age of an object in comparison with another object. This also means that it is not necessary for this purpose to determine the absolute age of the objects, but instead the age of one one of them is compared with another one, and we get to the relative dating of an object that is required.

an angle + its complement = 90 degrees