Answer: I believe the right answer is B) atmospheric nitrogen→bacteria→plants→animals. I'm pretty sure!
Sorry for answering a bit late, hope that helps! :-)
The first top one is right

<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>
Their will be fewer competitors in the new habitat