C the presence of harmful substances in food
It changes the way the earth looks and the resources we are available to

<em><u>Nitrogen</u></em><em><u> </u></em><em><u>is</u></em><em><u> </u></em><em><u>not</u></em><em><u> </u></em><em><u>a</u></em><em><u> </u></em><em><u>product</u></em><em><u> </u></em><em><u>of</u></em><em><u> </u></em><em><u>photosynthesis</u></em>
Seasonal changes occur because of earth's tilt
Answer: I think it was Richard Nixon.
I'm not completely sure about it, but I hope this helps!! :)