Answer :
Final answer:
The atomic number of an element is equal to the number of protons, which for the element described is 82, corresponding to choice D. 82.
Explanation:
An element X has 127 neutrons and 82 electrons. Its atomic number is 82. To determine the atomic number, we look at the number of electrons, which is equal to the number of protons. In this case, the element X has 82 electrons, which means it also has 82 protons, making its atomic number 82. Therefore, the correct answer is D. 82.
