Final answer:
The chain of fusion reactions is called the proton-proton chain. Larger stars undergo the triple-alpha process, and hotter stars use the CNO cycle.
Step-by-step explanation:
The chain of fusion reactions leading from hydrogen to helium that powers main-sequence stars is called the proton-proton chain or proton-proton cycle.
In stars that are larger and heavier than our sun, the dominant nuclear reaction is called the triple-alpha process. In this process, helium nuclei fuse to eventually form carbon.
In hotter stars, another set of reactions called the carbon-nitrogen-oxygen (CNO) cycle accomplishes the same net result. In the CNO cycle, carbon and hydrogen nuclei collide to form nitrogen, oxygen, and ultimately, helium.