How where heavier elements such as carbon and oxygen formed?

Depending on the size of the star, the core compression after each elemental fuel type is used up may or may not produce a temperature which allows the next fusion scenario to proceed.

For Deuterium, it is about 1 million K; for Hydrogen it is about 4 million K and for Helium it is 100 million K. These are big jumps.

Our Sun will burn Hydrogen and then Helium. It does not have enough mass to compress the core and heat it to burn Carbon.

In Stars above 8–10 Solar masses, they will be able to run through all the elements available for fusion until it gets halted by Iron, as fusing Iron requires more energy than it gives out.

Hydrogen fusion produces mainly Helium during the process, if the proton-proton method is prevalent, or also some Carbon and Oxygen and Nitrogen if the CNO path is used

explanation:

venn diagram is pictorial representation with of circles showing the relation between two finite sets or things. the intersection part of two circles conveys the relation present in between those sets or things.

here in the venn diagram of sand and salt two circles represent sand and salt. but the area falling under the intersection of these circle represents the mixture of sand and salt.

so, in a venn diagram the mixture will be placed in a middle that is in between the intersection of two circles.