What are CD4 cells? A. HIV treatment cells B. T cell helpers that are destroyed by HIV C. experimental AIDS vaccine D. Opportunistic cells that destroy the immune system

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

Which would be the most useful source of evidence to support mcneill's contention?

Me the formula cacl2 represents the compound