Which one of the following is FALSE about cache memory?

a$.$ On$-$chip CPU cache is used because main memory accesses are expensive.

b$.$ A CPU request for a memory object may hit or miss in the on$-$chip CPU cache.

c$.$ On$-$chip CPU cache contains a subset of data that resides in main memory.

d$.$ The hit rate of an on$-$chip CPU cache impacts the correctness of programs.

e$.$ On$-$chip CPU cache exploits temporal and spatial locality in programs.