What are the nucleotides of RNA made of?

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

Wich is not standing in the way of astronomers getting a good view of different star

Lupe is a carrier for color blindness. her husband clifford is colorblind. if lupe and clifford have four children, what's the probability of a boy being colorblind?