Which of the following are propagation steps in the free radical monochlorination of methane?

A propagation step consumes one radical and produces another. The first two steps do this. $\mathrm{Cl}{}_2\to 2\mathrm{Cl}{}^{\bullet }$ is initiation because it creates radicals from a molecule, and $\mathrm{CH}{}_3{}^{\bullet }+\mathrm{Cl}{}^{\bullet }\to \mathrm{CH}{}_3\mathrm{Cl}$ is termination because two radicals are consumed. Answer: 1 and 2.