The $$proton$$proton chain$$ of nuclear reactions drives much of the Sun$$s nuclear

fusion.

$($a$)$ Which atomic nucleus is used to start the reaction?

A $1$H

B $2$H

C $3$H

D $3$He

E $4$He

$($b$)$ Which atomic nucleus is the final product?

A $1$H

B $2$H

C $3$H

D $3$He

E $4$He