3. describe how the relative proportion of hydrogen, helium, and heavier elements will change as the sun ages.

The fusion of hydrogen makes helium in the Sun and as it collapses in the core internally it starts fusing heavier elements and transforms into Red Giant star.  

Explanation:

Almost all the stars in the universe is considered the main stream star as the atoms of hydrogen in its core fuses and forms helium . The longevity of these stars is dependent on the amount of materials in it or the massiveness of the star.

As the hydrogen fusion takes place in sun it helium is produced, the large helium atoms then converts into large atoms. However, the core of the sun starts fusing heavier elements as the sun ages and takes the form of Red Giant star.  

it has one origin of replication, but it proceeds in two directions - d)

i believe the answer is a or 1