Which atmospheric layer is where earth's northern and southern lights occur? mesosphere stratosphere thermosphere troposphere

Which of the following statements is true of enzymes? a)they dont provide an active site for substrates to bind in a reaction b)they act on a specific type of substrate in a reaction c)they unusable after a reaction d)they change shape after a reaction

Which statement is true about the cell theory? a) it is well-supported by evidence. b) it is unchangeable and permanent.

Many people try to eliminate fat from their diets. which is one reason it is necessary for humans to eat fat? a. eating fat is the fastest way to get energy. b. fat eliminates triglycerides from the body. c. saturated fats clear out the blood vessels. d. fat nerves transmit signals. , this is for apex in summer school.