1-chlorobutane and 1-iodobutane each undergo reaction with aqueous sodium hydroxide through a nucleophilic substitution mechanism. Under identical conditions, which reaction occurs at the highest rate, and what mechanism is used by that reaction?
- A1-chlorobutane, $S_N1$
- B1-chlorobutane, $S_N2$
- C1-iodobutane, $S_N1$
- D1-iodobutane, $S_N2$