Carbon in the atmosphere occurs primarily in what form?

Carbon in the atmosphere occurs primarily in carbon dioxide. The atmosphere contains about 750 billion tons of carbon in the form of CO2. Carbon dioxide (CO2) is an important trace gas in Earth's atmosphere currently constituting about 0.04%. Hope this helps.

Here's a link that can help you.. or search it on the internet... or leave the answers below. 

https://quizlet.com/41089439/ch-29-protist-fungi-flash-cards/
https://quizlet.com/2382668/biology-flash-cards/
http://highered.mheducation.com/sites/0072437316/student_view0/chapter30/chapter_quiz.html