Two sound waves of equal amplitude interference so that compression of one wave falls on the rarefaction of the other. which statement is true?
a. no sound is heard
b. the loudness of the sound increase
c. there is no change in the sound
d. the pitch of the sound increases

Assume that a person skiing high in the mountains at an altitude of h = 15100 ft takes in the same volume of air with each breath as she does while walking at sea level. determine the ratio of the mass of oxygen inhaled for each breath at this high altitude compared to that at sea level. assume that the air composition (i.e. % of air that is oxygen) is the same at sea level as it is at 15100 ft.

Energy flows from the producer level to the level. is called

Why does karst topography exist in some geographic location? a. few climates have enough oxygen b. most regions have rock layers other than limestone c. in most regions, the soil is too thin d. the water is too acidic enough in most places