A student set up a controlled experiment to investigate the conditions needed for germination. She placed moist cotton wool and soaked alfalfa seeds in two large sealed flasks. Flask A contained sodium pyrogallate solution, which absorbs oxygen from the air. Flask B contained sodium hydroxide solution, which absorbs carbon dioxide from the air. After 24 hours, she found that the seeds had germinated in flask B only.

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the answer is 100% density i've answered this question before and done the quiz myself.

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.