Answer: C) The net force on the brick is 0 N, and the brick remains at rest.
So first we need to know what the formulas are:
Methane: 
Oxygen: 
Carbon Dioxide: 
Water: 
So then we follow the equation as specified in the question. Note that it does not need to be balanced, as the question states it wants the unbalanced equation:
→ 
This is the preliminary, unbalanced equation with the correct chemical formulas.