When climbing a high mountain you get out of breath easily because...
A) the percentage of nitrogen in the air falls
B) the air is more dense
C) there is less oxygen in each cubic meter of air
D) the air pressure is greater

Which of the following is the most likely result of converting forestland to urban development? a.the amount of land available for lumber production decreases. b.fewer trees are needed because cities are made mainly of concrete. c.people discover more efficient ways to grow trees. d. the price of lumber goes down.

Which two criteria must be met before scientist can use radiocarbon dating? explain your answer

Amines amides and amino acids are categories of