The molar mass of a substance is the mass of one mole of that substance. Therefore, in order to calculate the mass that is present while the number of moles are known, we simply multiply the number of moles present by the molar mass. In the case of carbon dioxide, the molar mass is obtained by adding the mass of one carbon atom (12) and two oxygen atoms (32). The molar mass is 12 + 32 = 44. Therefore, the mass of carbon dioxide is 2.1 * 44 = 92.4 grams. The answer is D.