Which is true for a shotgun but not for a rifle or a handgun?

The projectiles are pellets.

A shotgun has lands and grooves in the barrel.

A shotgun shell does not use a primer.

Shotguns do not have firing pins.

This actually depends. The last two are wrong no matter what. But some handguns and rifles have shotshell loads, so they can shoot pellets. A shotgun can shoot rifles slugs. So the best answer is the first one, but not really true