One mole of CO2 contains:

A. 3 gram atoms of CO2:
- To determine the number of gram atoms in one mole of CO2, we need to calculate the molar mass of CO2.
- The molar mass of carbon (C) is 12.01 g/mol, and the molar mass of oxygen (O) is 16.00 g/mol.
- Therefore, the molar mass of CO2 can be calculated as follows:
Molar mass of CO2 = (12.01 g/mol) + 2(16.00 g/mol) = 44.01 g/mol
- One mole of CO2 contains 44.01 grams of CO2, which is equivalent to 3 gram atoms of CO2.

B. 18×10^23 CO2 molecules:
- Avogadro's number (6.022 × 10^23) represents the number of particles in one mole of a substance.
- In one mole of CO2, there are 6.022 × 10^23 CO2 molecules.
- This means that if we have 18×10^23 CO2 molecules, we have exactly one mole of CO2.

C. 6×10^23 O atoms:
- In one molecule of CO2, there are two oxygen (O) atoms. Therefore, in one mole of CO2, there are twice as many oxygen atoms.
- Since one mole of CO2 contains 6.022 × 10^23 CO2 molecules, which have a total of 2 × 6.022 × 10^23 = 12.044 × 10^23 oxygen atoms.
- This can be approximated to 6 × 10^23 oxygen atoms.

D. 6×10^23 C atoms:
- In one molecule of CO2, there is one carbon (C) atom. Therefore, in one mole of CO2, there is one mole of carbon atoms.
- Since one mole of any substance contains 6.022 × 10^23 particles, there are 6.022 × 10^23 carbon atoms in one mole of CO2.
- This can be approximated to 6 × 10^23 carbon atoms.

In summary, one mole of CO2 contains 3 gram atoms of CO2, 18 × 10^23 CO2 molecules, 6 × 10^23 oxygen atoms, and 6 × 10^23 carbon atoms.