Which of the following compounds liberate hydrogen on treatment with sodium metal?

Sodium reduces any sufficiently acidic X-H bond to H2. But-1-yne (terminal sp C-H, pKa about 25), ethanol (15.9) and phenol (10.0) all react to give the sodium salt. But-2-yne has no acidic sp C-H bond, and its sp3 C-H bonds are far too weak as acids, so there is no reaction.