How is oxygen added to the air? a)plants release oxygen as a waste product of photosynthesis. b)animals release oxygen as a waste product of respiration. c)oxygen is released from the burning of fossil fuels, such as coal. d)oxygen is released by plants as a waste produce of respiration.

Put the following steps of the convection process in the correct order. 1. gravity pulls cooler matter downward. 2. the matter expands and decreases in density. 3. an up-and-down flow of matter produces a convection current. 4. matter is heated. 5. warmed matter is forced upward. question 2 options: a) 4, 2, 5, 1, 3 b) 2, 4, 3, 1, 5 c) 3, 2, 5, 4, 1 d) 1, 4, 2, 5, 3

What is the next step in muscle contraction after the actin changes shape? (apex)

When the cell concentrates potassium within, against the natural tendency of matter, it is performing a.passive diffusion b.facilitated diffusion c.active transport d.pinocytosis