If you mean which isotope, then carbon-12 is the most abundant. If you mean where does the carbon come from, then it's atmospheric carbon dioxide for plants, and food for animals.
I don't know what a macromolecule is, but carbon is most associated with living things. Eg "carbon-based life-form"
A majority of the earths carbon is located in the ocean.
Carbon-12 is the most common form of Carbon and therefore, counts for most of the atomic mass.
Carbon, oxygen and nitrogen most often form multiple bonds.
CH4, which is the most reduced form of carbon.
Most of the Earth's carbon is located in the atmosphere. It is in the form of carbon dioxide
A majority of the earths carbon is located in the ocean.
In the atmosphere, in the form of carbon dioxide
Carbon, hydrogen, nitrogen and oxygen (in no particular order).
I don't know what a macromolecule is, but carbon is most associated with living things. Eg "carbon-based life-form"
Most of the carbon in the atmosphere is in the form of carbon dioxide, (CO2) gas.
The thing about carbon is that it can form all kinds of carbon-carbon chains; this allows lots of interesting compounds, especially proteins, and a solution of proteins in water is fundamental to all life (as we know it).
In the atmosphere, in the form of carbon dioxide
In the atmosphere, in the form of carbon dioxide
The bonds that carbon form are the most important charicteristic.
While most carbon compounds are completely safe and in many cases necesarry for life as we know it, there are some carbon compounds or carbon molecules that are carcinogenic (cancer causing), and others that can form into highly toxic chemicals (cyanide is one of these).
Diamond.