Select the most appropriate option to substitute the bracketed segment in the given sentence. If there is no need to substitute it, select 'No substitution required'.
That is not a solution available (to most people for who email has become necessity.)

A

to most people for who email has become a necessity.

B

to most people for whom email has become a necessity.

C

for most people to whom email has became necessity.

D

No substitution required