A mixture of C 3​ H 8​ (g) & O 2​ having total volume 100 ml in an Eudiometry tube is sparked & it is observed that a contraction of 45 ml is observed what can be the

C3​H8​(g)+5O2​(g)→3CO2​(g)+4H2​O(l)

As par above equation 1 mole of porpane reacts with 5 moles of oxygen to form 3 moles of carbon dioxide.

We know that the number of moles is directly proportional to the volume of the gas.

Thus when 15 ml of propane reacts with 75 ml of oxygen, 45 ml of carbon dioxide will be obtained.

The contraction in the volume will be $15+75-45=45ml$.

This is possible when the composition of the reacting mixture is either 15ml C3​H8​ and 85ml O2​ or 25ml C3​H8​ and 75ml O2​.

Hence, options A and B are the correct answers.