How many variables can a scientist change during a scientific investigation?

What are the doorways into and out of cells, attached to the membrane, and built in the rough er.

Waianapanapa beach in hawaii is a black-sand beach that was formed by waves crashing against volcanic rock. the sand can be very hot on sunny days. which statement best explains why? o a. the black sand has no heat capacity. b. the black sand absorbs no radiation. o c. the black sand is immune to insolation. d. the black sand has a low albedo.

If animal agriculture was eliminated, how much grain would become available for human consumption?