Step 1: Understand the Monomers of Bakelite and Melamine - Bakelite and Melamine are both thermosetting polymers, and both are made by the polymerization of formaldehyde (methanal). - Bakelite is formed by the reaction of phenol with formaldehyde, while Melamine is made by polymerizing melamine (a nitrogen-rich compound) with formaldehyde.
Step 2: Identify the Common Monomer - The common monomer for both Bakelite and Melamine polymers is formaldehyde (methanal), which reacts with different monomers (phenol for Bakelite, melamine for Melamine) to form the respective polymers. Hence, the correct answer is methanal.