Question

question 15
while on the main sequence, stars may generate energy through
nuclear fusion of he into c
the triple alpha process
the proton - proton chain or the cno cycle
nuclear fusion of c into o

Explanation:

Stars on the main - sequence generate energy mainly through the proton - proton chain (in lower - mass stars) or the CNO cycle (in higher - mass stars). The triple alpha process and nuclear fusion of He into C or C into O occur in later stages of stellar evolution, not primarily on the main sequence.

Answer:

the proton - proton chain or the CNO cycle