The answer is Gravity. To ensure the one-way flow of blood the veins contain a network of valves which arteries do not have. The reason is for the veins to counteract the force of gravity on flow of blood. For example, to increase the pressure of the blood back to the heart the veins must counteract the force of the gravity.
Answer: A) gravity
Explanation: I Took The Pre-Test On US Test Prep.
Answer:
Explanation:
Enzymes don't take part in a reaction but just speeds up a reaction
A baseline for an experimental investigation is provided by the
⇒ control group .
this is the correct answer. i am 100% positive
if its 12, 10, and 8, then the answer is Z, X, Y