Which statement is correct regarding elementary particles and nuclear radiation characteristics?

Introduction / Context:
Basic nuclear and particle physics concepts include particle identities and comparative properties of emitted radiations (alpha, beta, gamma). These properties determine ionisation behavior, penetration, and detection methods, which are central to radiation protection and instrumentation.

Given Data / Assumptions:

• We compare truthfulness of statements about positrons and the relative characteristics of alpha, beta, and gamma radiation.
• Vacuum propagation speeds and ionising abilities are standard textbook facts.
• No computation is necessary.

Concept / Approach:
The positron is indeed the electron's antiparticle; it has the same mass but positive charge. Alpha particles (helium nuclei) are massive and doubly charged, leading to very high ionising power but low penetration and speeds well below light. Beta particles are electrons or positrons with lower ionising power than alpha but higher than gamma in many media. Gamma rays are uncharged photons and move at light speed in vacuum, exhibiting the greatest penetration and least ionising power among the three on a per-path basis.

Step-by-Step Solution:
Check particle–antiparticle relation: positron ↔ electron (true).Assess alpha decay effect on neutron/proton: both N and Z decrease by 2; the ratio does not increase markedly and can slightly decrease for heavy nuclei.Compare ionising powers: alpha > beta > gamma; statement that beta exceeds alpha is false.Speeds: gamma travels at c; alpha cannot exceed this; thus the claim alpha faster than gamma is false.Charge of gamma: photons are neutral; claiming opposite charge to electrons is false.

Verification / Alternative check:
Introductory nuclear physics tables list positron as e+ and confirm the qualitative ordering of ionisation and penetration for alpha, beta, gamma radiations.

Why Other Options Are Wrong:
Alpha decay increasing N/Z markedly: not generally correct; both N and Z drop by 2.Beta ionising > alpha: reverses the usual order.Alpha faster than gamma: impossible; gamma travels at the speed of light in vacuum.Gamma charged: incorrect; gamma photons are neutral.

Common Pitfalls:
Confusing penetration with ionisation. High ionisation (alpha) does not mean high penetration; in fact, it usually implies the opposite due to rapid energy loss.

Final Answer:
A positron is the antiparticle of an electron.