Why are people gay and how can they even turn gay?

Which of the following claims does the author support the least

Nucleic acid certain protein cell membranes certain carbohydrates

What did not occur in the proterozoic eon a)the oxygen levels increase greatly in the atmosphere,b)the emergence of the eukarya , c)muti cella’s eukaryotic organisms began to diversify,d)anaerobic bacteria kept thriving with more oxygen