Which is a characteristic of nuclear fusion but not nuclear fission?
a. releases large amounts of energy
b. is the energy source of stars
c. is used in electric power plants
d. requires little energy to occur

b. is the energy source of the stars

Explanation:

Nuclear fusion occurs when two nuclei combine to form a single atom for example two individual hydrogen atoms combine to form a single Helium atom. Nuclear fission involves a relatively larger nucleus splitting into smaller nuclei for example a uranium-235 splitting into barium-141 and krypton-92 which releases energy. However, fusion releases higher amount of energy in comparison to fission. Fusion occurs majorly in stars like our sun and is responsible for the energy emitted by them.

gravity causes stares to cluster i think so