partial pressures...can someone please explain why, assuming you also know the correct answer. Thank you much

Question

the reaction system: CS2 (g) +4H2 (g) yields CH4 (g) +2H2S(g) is at equilibrium. What would describe the behavior of the system if the partial pressure of hydrogen is doubled? As equilibrium reestablishes, would the : a) pressure of CS2 increase, b) pressure of CH4 decrease, c) pressure of H2 decrease, d) pressure of H2S decrease, or e) all the pressures will decrease???

Answer 1

CS2 (g) +4H2 (g) <----> CH4 (g) +2H2S(g)

a) pressure of CS2 increase, - NO
b) pressure of CH4 decrease, - NO
c) pressure of H2 decrease, - YES
d) pressure of H2S decrease, - NO
e) all the pressures will decrease - NO