In this sentence we would be looking for a word which best expresses "Tantamount" from the given options
Tantamount means equivalent in seriousness to; virtually the same as. This makes it synonymous to equal.
If we look into the other options,
Cause means a person or thing that gives rise to an action, phenomenon, or condition
Result means a thing that is caused or produced by something else; a consequence or outcome
Repetitious means another term for repetitive
Option C is correct