<h2>
Answer:</h2>
The nuclei with <u>D. 1 proton and 2 neutrons</u> will be least stable.
<h2>
Explanation:</h2>
Nuclides containing odd quantities of the two protons and neutrons are the least steady and this implies increasingly radioactive.
Nuclides containing even quantities of the two protons and neutrons are most steady and this implies less radioactive.
Nuclides contain odd quantities of protons (positive charged particles) and even quantities of neutrons are less steady than nuclides which are containing even quantities of protons and odd quantities of neutrons. By and large, atomic strength is more prominent for nuclides containing even quantities of protons and neutrons or both.
When we add 1 proton with 2 neutrons we get 3 as answer, which means an odd value, thus nuclide with this proportion of proton and neutron is least stable.
