What do you notice about the temperature on the x-axis of the H-R
diagram?
A. It increases from left to right
B. It increases from right to left
C. It increases from bottom to top
D. It increases from top to bottom
Madsciencelessons. com 2015

because u need two or more forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei to form isotopes.

so since they all have the same shape? i mean maybe because m& m and reeses are both chocolates