Question

When a star enters the red giant stage it begins to convert ________ to _________ in its core.

Answer 1

A. 
hydrogen; helium
is the right answer

Answer 2

Answer: The correct answer is Option c.

Explanation:

Red giant stage of the star is known as the dying star which is the last stages of stellar evolution.

When the core of the star runs out of hydrogen, it no longer produce radiation to balance out the weight of the star.  The star will get collapsed, the core will also get contract and hence, the temperature will increase.

When the temperature of the core increases, this temperature is enough for the nuclear fusion of helium to carbon atom by a process known as 'triple-alpha process'.

The equation representing the fusion process follows:

$_2^4\textrm{He}+_2^4\textrm{He}\rightarrow _4^8\textrm{Be}+\gamma\\\\_4^8\textrm{Be}+_2^4\textrm{He}\rightarrow _6^{12}\textrm{C}+\gamma$

Thus, the correct answer is Option C.