Why do some areas have more acid rain in other places

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

Hemoglobin is a proton that carries oxygen around the body what is hemoglobin made from

In which part of the body is a ball-and-socket joint found?