Answer: B
2-Methylbutane has four kinds of equivalent hydrogen: the six hydrogens of the two equivalent methyls on C-2, the single tertiary hydrogen, the CH2 hydrogens, and the terminal CH3 hydrogens. Each gives a different monochloride: 1-chloro-2-methylbutane, 2-chloro-2-methylbutane, 2-chloro-3-methylbutane and 1-chloro-3-methylbutane (RDKit count: 4).