Light nuclei like hydrogen have slightly less binding energy per nucleon, so their mass per nucleon is slightly greater than that in heavier nuclei such as oxygen.

The Lyman series (transitions to n=1) lies in the ultraviolet region of the spectrum.

Joining light nuclei to form a heavier nucleus is nuclear fusion; fission is splitting a heavy nucleus.

Combining small molecules into large chain-like molecules is called polymerization.

Number of neutrons equals mass number minus atomic number, i.e., M - Z, so option A is correct.

Gamma rays are high-energy electromagnetic radiation and are more penetrating than alpha, beta or X-rays.

19 days = 5 half-lives, remaining fraction = (1/2)^5 = 1/32; 10.38/32 ≈ 0.324 ≈ 0.32 gm.

If electrons reach n=4 (third excited state), the number of possible emission lines between levels up to n is n(n−1)/2 = 4×3/2 = 6.

The question as printed expects 'Fundamental' as the intended answer in this context (common textbook phrasing).

Fusion requires overcoming electrostatic repulsion between nuclei, which demands very large input energy (high temperature), so option C is correct.