SC.7.N.1.4 10. Which scientific investigation does not include Dependent (outcome) and
Independent (test) variables?
A) counting bird populations I
B) studying the effect of temperature on bacterial reproduction rates
C) investigating the effect of mass on the speed at which an object falls
D) testing a model car in a wind tunnel to minimize air flow resistance and maximize
fuel economy

b. the carbon cycle ensures living things have a source of hydrogen

the correct answer is b

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.

this is more of a statement than a question. is there answers to go along with this, or is it opinion based?