The nucleus of one atom contains 12 protons and 12 neutrons, while the nucleus of another atom contains 12 protons and 16 neutrons. What are the atoms? A) chromium atoms
B) two different elements
C) two isotopes of an element
D) negatively charged

Option C (two isotopes of an element)

Explanation:

An isotope is two or more forms of the same element that contain equal numbers of protons (as well as electrons) but different numbers of neutrons in their nuclei, and hence differ in relative atomic mass but not in chemical properties. For example :-

Isotopes of carbon ⇒

In the question , both the atoms have same number of protons , but their number of neutrons isn't same. Hence , they are the isotopes of an element.

i think the answer is terrae but not 100 percent sure. ▓▬▬ §