CPA Network Reply Email?

Just got this email from one of the CPA networks I applied to. Not really sure how to answer it. Can any help or shed some light?

"We received your application to *********. Right now, we are email-oriented with our proprietary CPCs, but will be expanding into content/display in the near future. Please let me know what verticals you can get placed immediately as we would like to discuss being one of your advertising sources. Thank you."

they are asking you which niches you want to promote..
vertical being the niche itself..

if for example you would like to promote health stuff tell them something like

I am interested in your health verticals and would love to see the offers you have for me.

or think of something yourself now that you know what verticals are

Just use some basic stuff, like health niche, email submits, sports niche etc.

go with micro niche site. this will convert well