Which of the following are relative?

A. Time only

B. Time, length, and mass

C. Time and mass

D. Time and length

Answer: D. Time and length

Explanation.

Time is always measured relative to some reference time, so it is relative.

Mass is the matter that defines an object. It could be converted into energy but its quantity does not change, so it is not relative.

Length is a measurement that is compared against a standard, so it is relative.