Which of the following correctly contrasts nucleophilic acyl substitution with nucleophilic addition in step-growth polymerization?

Both mechanisms exclusively form carbon-carbon bonds.

Nucleophilic addition involves the loss of a leaving group.

Nucleophilic acyl substitution and nucleophilic addition are identical in their mechanisms.

Nucleophilic addition involves the formation of carbon-carbon bonds, while nucleophilic acyl substitution involves the formation of carbon-heteroatom bonds.