What is the importance of water on earth?

a) it keeps the top layer of the geospere cool
b) it allows life to exist

c) it provides ice at the poles

d) it creates earths blue color from space

How have the greenhouse gasses increased from the year 2000 to 2018

How does the atmosphere to make earth livable? check all that apply. causes the seasons contains oxygen provides warmth creates important nutrients blocks harmful energy from the sun plz like !

Tooth enamel consists mainly of the mineral calcium hydroxyapatite, ca_10(po_4)_6(oh)_2. trace elements in teeth of archaeological specimens provide anthropologist with clues about diet and diseases of ancient people. students at hamline university measured strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. solutions with a constant total volume of 10.0 ml contained 0.726 mg of dissolved tooth enamel plus variable concentrations of added sr. added sr find the concentration of sr in the 10 ml sample solution in parts per billion = ng/ml. find the concentration of sr in tooth enamel in parts per million = mu g/g.