The difference between ''1 C atom and 1 mole of C atoms"?

[Indranil]

Does 1 C atom mean a single C atom of 6.023 X 10^23C atoms = 1 C atom of Avogadro's number of C atoms = 1 C atom of 6.023 X 10^23 numbers of C atoms?
Does 1 mole of C atoms mean Avogadro's number of C atoms = 6.023 X 10^23 numbers of C atoms?
I am confused. What is the difference between them (1 C atom and 1 mole of C atoms)? Could you clarify it, please?

[Elric]

The first question I don’t understand. The second question is correct. As to the third question, do you mean 1C as in a formula?

[FISMAQUIM]

A swimmer breathes twenty times a minute and inhales 200 mL of air with each breath. Consider that inhaled air contains 20% (v/v) of O2(g) and the exhaled air has 10% of O2(g). If all consumed oxygen was used in the body's combustion of glucose and 25% of the energy obtained was used in the muscular work relay, determine the maximum distance that this swimmer to go in 1 hour, considering that 100 kJ of energy is spent in each km.
Data: ΔHº(combustion) of glucose = -2880 kJ/mol, body temperature equal to 37°C.
Answer: 1,1328 km