Answer:
You could be made of t-rex breath,
Step-by-step explanation:
Mentioned carbon cycle and photosynthesis are what will give your answer more detail, here's an example paragraph with basic information:
It's plausible that you or I could potentially be made of T-rex breath; what exactly do I mean by that?
To begin we'd have to think back to when T-rexes were alive and believe it or not plants weren't too different then, just like todays plants take in carbon dioxide from the air and change it to oxygen through photosynthesis-- they (plants) got this carbon dioxide not only from the air but from animals that would exhale it; for example, the t-rex which more likely than not exhaled a lot of carbon dioxide, and all of it didn't just get inhaled immediately by plants sometimes sticking around in the atmosphere.
Although a lot of plants and t-rex eventually went extinct or burned up from the asteroid it's not to say that the carbon didn't linger in the atmosphere, get absorbed into the water, grow a plant, and then get released into the atmosphere once again; this is known as the carbon cycle and it happens continuously over an undefined amount of time, eventually, that grass that unknowingly carries ancient air could be eaten by a grazing animal such as a cow which in turn becomes your hamburger. Needless to say, saying you're 'made of t-rex breath' is overexaggerating, but while unlikely it is possible anyone could be breathing in air that's been circling the earth for millions of years.
It really didn't need to take me this long to answer I apologize- good luck!