Which of the following sets of characteristics describe what we know about the inner planets?
select one:
a. they are closest to the sun, have many moons, and include ring systems.
b. they are closest to the sun, have many moons, and include ring systems.
c. they have rocky surfaces, no rings, and few or no moons.
d. they have rocky surfaces, ring systems, and are larger in size.

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.