2) B

A – Wrong
Bromine water is the test for the presence of alkenes.

B – Correct
A burning splint makes a popping sound in hydrogen, goes out in carbon dioxide and then the glowing splint relights in oxygen. 

C – Wrong
Limewater turns milky in the presence of carbon dioxide. However, no observations are made in the presence of hydrogen and oxygen. 

D – Wrong
This is the test for acids. Blue litmus turns red in acid.

E – Wrong
This is the test for alkali. Red litmus turns blue in alkali.