If it's for a school report, the history of the B might be a bit hard to trace... it began somewhere in the early 80's, noone outside of Japan is quite sure when.

The first of the modern B's was most likely the B16A (most notable as the first Honda 100hp/litre engine) but could also have been the B18A. The B18A's valvetrain is very similar to the DOHC ZC series, etc. with the interesting facts.

What exactly is the report for? There's a lot of material to cover, ten pages easy for an abbreviated version.