Isobutane (2-methylpropane) undergoes monohalogenation. Which of the following statements are correct? (Relative reactivity per H in chlorination: primary : tertiary $=1:5$.)

1. AChlorination gives more 1-chloro-2-methylpropane than 2-chloro-2-methylpropane
2. BBromination gives 2-bromo-2-methylpropane almost exclusively
3. C$\mathrm{Cl}\cdot$ abstracts hydrogen with an early transition state and is less selective than $\mathrm{Br}\cdot$
4. DBromination of ethane is faster than chlorination of ethane under the same conditions