The answer is D. The cold fusion theory was first brought about by Stanley Pons and Martin Fleischmann in 1989. They claimed that their unintended experiment has produced enormous amounts energy at room temperatures that could only be explained by cold fusion theory. The experiment involved the electrolysis of heavy water (with deuterium rather than hydrogen isotope) on a palladium (Pd) electrode. Their claims had brought immense attention by scientists, however, subsequent replicative experiments attempts failed and some discredited the initial experiment.
From the Graham's law of effusion;
R1/R2 = √MM2/√MM1
Molar mass of chlorine gas is 71
Therefore;
1.87= √ 71 /√mm1
= 1.87² = 71/mm1
mm1 = 71/1.87²
= 71/3.4969
= 20.3
Thus, the molar mass of the other gas is 20.3 , and i think the gas is neon