Tony, a sales manager at OmniEye, presents his company's new range of advanced surveillance cameras to a group of prospective buyers. Tony claims that the company's new version of cameras have a zoom capacity $10$ times greater than its previous version. In the context of verbal support elements, Tony uses a$($n$)\_\_\_\_\_$ to enhance his presentation.

a$.$ product demonstration

b$.$ anecdote

c$.$ example

d$.$ testimonial

e$.$ case history

f$.$ none of the above