Here's a problem to solve: An unbalanced equation for the reaction of methane gas (CH_{4}) with oxygen is shown below. CH_{4} + \Box O_{2} -> 2CO_{2} + 4H_{2}O How many molecules of oxygen gas (O_{2}) are needed to properly balance this equation?

Among the 4 following options, which is the correct answer?

- A: 1
 
- B: 2
 
- C: 3
 
- D: 4
 