Final answer:
Before applying latex paint to new drywall, a primer should be used to seal the porous surface, improve adhesion, and provide a uniform finish. It also serves to block stains and enhance paint durability.
Step-by-step explanation:
The product that should be used before applying latex paint to new drywall is a primer. Priming new drywall is crucial because it seals the porous surface of the drywall, which allows the topcoat of paint to adhere better and provide a uniform finish. Without priming, the paint may soak into the drywall, leading to poor coverage and potentially necessitating more coats of paint. Using a primer also helps to block stains and can improve the overall durability of the paint job.