For the addition of $\mathrm{HBr}$ to buta-1,3-diene, which statement is correct?

1. AAt $40^{\circ }\mathrm{C}$ the 1,2-adduct predominates because its double bond is more substituted
2. BAt $-80^{\circ }\mathrm{C}$ the product ratio is decided by the relative stabilities of the two products
3. CThe 1,4-adduct is thermodynamically more stable because its double bond is disubstituted (internal)
4. DThe 1,2- and 1,4-adducts arise from two different carbocation intermediates