The changes in the direction of a current flow in a system using alternating current are based on the of the system A. voltage
B. frequency
C. amperage
D. phase

you would expect a sound wave to speed up. - b)

the answer is a. at the equator

the earths atmosphere is made up of nitrogen and oxygen. solids can turn into gasses through a process called sublimation. sublimation is the transition of a substance directly from the solid to the gas phase, without passing through the intermediate liquid phase.

hope this : d