If the neutron-to-proton (n/p) ratio in a nucleus equals 1, the nucleus is said to be:

The correct answer is Option A — Stable. When the neutron-to-proton (n/p) ratio equals 1, the nucleus is stable. This means there is a balanced number of neutrons and protons, which is the most stable configuration for lighter nuclei. Option B (Unstable): An unstable nucleus has an n/p ratio that deviates from 1. Option C (Radioactive): Radioactive nuclei have imbalanced n/p ratios and undergo decay. Option D (Fissionable): Fissionable refers to nuclei that can split under neutron bombardment (like Uranium-235).