(image attached) what mistake did carl make?

A) He did not multiply with calcium atoms by the subscript 2.
B) He did not add the coefficient 4 to the chlorine and oxygen atoms.
C) He did not add the subscript 2 to the calcium atoms.
D) He did not multiply the chlorine and oxygen atoms by the coefficient 4.

(pls answer question with letter choice as well as explaination)

D) He did not multiply the chlorine and oxygen atoms by the coefficient 4.

Explanation:

The coefficient 4 at the beginning of the chemical formula indicates that there are four Ca(ClO3)2 molecules. Think of this as Ca(ClO3)2 × 4. This means that he had to multiply the number of atoms for each element by 4 as well, so he should've ended up with 4 total calcium atoms (which is correct), 8 total chlorine atoms, and and 24 total oxygen atoms. He did not get all these answers because he didn't multiply the chlorine and oxygen atoms by the coefficient 4.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.

it is reliable if two scientists recorded it