An air-filled balloon shrank when moved from a warm room to a refrigerator. Which statement BEST explains why the balloon shrank? A. The mass of the air decreased as the balloon cooled.
B. Internal pressure of the balloon decreased due to lower kinetic energy.
C. The volume of air decreased as the number of particles decreased.
D. External pressure on the balloon increased due to lower temperature.

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.