The antiparticle of the electron is the positron (a positively charged electron).

If the electron loses all its kinetic energy, the emitted photon has maximum possible energy, hence maximum frequency (fmax) and minimum wavelength (λmin).

Even-even nuclei typically have integral (often zero) spin, and the OCR shows a mark adjacent to option B.

Thorium undergoing beta decay produces protactinium; the OCR shows a tick next to Protactinium, so option A is indicated.

The reciprocal of the decay constant λ equals the mean lifetime (τ = 1/λ).

Block header indicates option B; the maximum kinetic energy expression is 1/2 mv^2 = hν - φ (represented here by Ve).

On going to higher n, potential energy becomes less negative (increases) and total energy becomes less negative (increases), so PE and TE both increase; option D is correct.

Average natural background radiation exposure is typically about 2 millisieverts per year.

The OCR indicates option A; dividing the total binding energy (1020.5 MeV) by 120 nucleons yields approximately 8.504 MeV, but the OCR-marked option in the text is A as given.

Fusion reactions of light nuclei release on the order of tens of MeV; the d+d→He reaction releases about 24 MeV total in typical branch accounting.