OCSP response query

Hi Guys,
When i get a ocsp response in http 200 ok message. I can see a field called certs. And this contains two items. What are the kinds of certificates returned in an OCSP response. And What public key has to be used to verify the signature on the response?
I am having trouble in identifying what kind of certificates are returned and How to verify the signature of the response. i.e which certificate public key can be used to verify the response.
TIA

have a read here : http://www.openssl.org/docs/apps/ocs..._verification_