For this problem, we are simply asked to convert from units of moles to units of mass. To do this, we need a factor to multiply to the original value. We will be using the molar mass of the compound. For CH4, the molar mass would be 16 g/mol. We do as follows:
mass = 0.35 mol CH4 ( 16 g / 1 mol) = 5.6 g CH4
Therefore, the correct answer is the second option.