Which scientific investigation does NOT include dependent and independent variables? Group of answer choices:

Investigating the effect of mass on the speed at which an object falls

Testing a model car in a wind tunnel to minimize air flow resistance and maximize fuel economy

Observing and counting birds

Studying the effect of temperature on bacterial reproduction rates

i believe your answer would be c.. : )

the nitrogen cycle provides nitrogen to the ecosystem from the atmosphere, ground and oceans. nitrogen is an important component of complex molecules such as amino acids and nucleotides, which lead to the creation of proteins and dna, the building blocks of all life. plants absorb nitrogen in the form of ammonium, nitrate ion and, on rare occasions, as amino acids. animals receive nitrogen necessary for biological processes from feeding on living or dead organic matter.