Step 1: Understand Novolac polymer.
Novolac is a phenol-formaldehyde resin formed under acidic conditions with excess phenol.
Step 2: Identify the monomers involved.
The two monomers required are phenol and methanal (formaldehyde). Their condensation leads to the formation of Novolac resin.
Step 3: Eliminate incorrect options.
Options involving ethanol or urea are incorrect, as they do not form phenol-formaldehyde resins.
Step 4: Conclusion.
Thus, the correct monomers used in the preparation of Novolac are phenol and methanal.