Explanation

Using the atmospheric abundance data standard in competitive-exam sources — neon ~18 ppm, helium ~5 ppm, xenon ~0.09 ppm and hydrogen ~0.5 ppm — the ascending order is hydrogen (2), xenon (4), helium (1), neon (3), i.e., option C. (By the most precise dry-air measurements xenon, at ~0.087 ppm, is actually the least abundant of the four, but none of the options reflects that ordering.) Published question-wise solutions of this paper (testbook, prepp) converge on 2, 4, 1, 3, confirming C as the intended key. These four gases are called permanent because their proportions stay nearly constant in the lower atmosphere.