The main memory of a computer has $2$ $cm$ blocks while the cache has $2c$ blocks. If the cache uses the set associative mapping scheme with $2$ blocks per set, then block $k$ of the main memory maps to the set:
option B) (k mod c) of the cache is the answer .
Shouldn’t the answer be $k\ mod\ 2c$ according to answer provided in https://gateoverflow.in/1442/gate2013-20. I agree that $k\ mod\ c$ is correct here. But both answers seem conceptually different to me.
In the Gate 2013 question link you provided, the question is kth block of MM is mapped to which cache line, whereas in this question it is asked kth block of MM is mapped to which cache set.