CallTalk Corporation, a phone calling service, uses its mark $$calltalk$$ as its domain name. Later, Converse Inc. uses the domain name $$caltalk$($a deliberate misspelling of $$calltalk$)$ without CallTalk$$s authorization, to sell sexually explicit phone conversations. This is an example of:

a$.$ a legitimate marketing technique.

b$.$ a fair use.

c$.$ a license.

d$.$ trademark dilution.