Jon likes hiking. he observes that whenever he hikes up a hill, he breathes heavier than when he is on flat ground. which two statements explain why this happens?

The correct statements are sensors in the brain predict the lack of oxygen and the muscles in his body require more energy and thus more oxygen.  

Whenever one goes on a level very high from the Earth's surface like in mountains, the sensors in the brain finds out that there is less oxygen present at a higher level. Secondly, whenever a person performs some kind of strenuous activity like mountain trekking, the production of lactic acid takes place in the muscles. Thus, the body needs more oxygen at that time to fulfill the requirement, due to the two mentioned factors the person breathes heavier.  

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.

some inherited genetic mutations can be good for the offspring, so the answer is different genetic mutations cause many forms of cancer.