Neutrinos (or antineutrinos) are emitted alongside electrons or positrons during beta decay.

The proton is about 1836 times more massive than the electron.

Hydrogen nuclei can be a single proton (protium), proton+neutron (deuteron), or proton+two neutrons (triton), so any of these.

Wavelength ~4460 Å falls in the visible range, which corresponds to the Balmer series (transitions to n=2).

Classical Larmor radiation estimates give a collapse time on the order of 10^-11 s for an electron spiraling into the nucleus, so option B is the classical estimate.

The block's provided answer key indicates option D; binding energies per nucleon are on the order of tens of MeV, so option D represents that magnitude per the OCR key.

Nuclear matter density is extremely high, about 10^14 g cm^-3 on the order of 10^14.

The block header indicates option A as the answer; for N bosons all occupying the single-particle ground state the total energy scales with N^3 in the given expression as per the provided choice.

All lumps decay with the same exponential factor, so their activity ratios remain unchanged at any future time.

An alpha decay reduces A by 4 and Z by 2; two beta decays increase Z by 2 with no A change, so the net Z is unchanged while A decreases by 4, producing an isotope (option B).