Which of the following is true of statistics as proof providers?

a$.$

They carry the lowest credibility when delivered from third$-$party sources.

b$.$

They are presented in the form of anecdotes.

c$.$

They are used in the form of statements from satisfied users.

d$.$

They are most effective when presented in a printed form rather than stated orally.

e$.$

They help prospective customers in establishing relationships with existing customers.