The reaction between hydrogen and oxygen to form water is given by the balanced chemical equation:

\(2H_2(g) + O_2(g) \rightarrow 2H_2O(g)\)

This equation tells us that 2 volumes of hydrogen react with 1 volume of oxygen to produce 2 volumes of water vapor.

In this case, you have 100 cm³ of hydrogen and 200 cm³ of oxygen. According to the stoichiometry of the reaction, the 100 cm³ of hydrogen would completely react with 50 cm³ of oxygen to form water.

Therefore, the volume of oxygen left unreacted would be the initial volume of oxygen minus the volume of oxygen that reacted:

Unreacted Oxygen = Initial Oxygen - Reacted Oxygen= 200 cm³ - 50 cm³= 150 cm³

So, the correct answer is 150cm³. This is the volume of oxygen that would be left unreacted after the explosion.