When testing hypotheses about two population means where ₁ and ₂ are unknown and no assumption is made about the equality of ₁ and 2, we use

A Normal distribution.

B Student t distribution with df = bigger of n₁ - 1 and n₂ - 1.

C Student t distribution with df = smaller of n₁ - 1 and n₂ - 1.

D Student t distribution with df = n₁ + n₂ - 2.