50 POINTS Which of the following correctly describes a compound?

A. The atoms are bonded together, and the compound has different physical and chemical properties than the individual elements.
B. The atoms have no set ratio for how the atoms can combine, and they are not chemically bonded together.
C. The atoms can only combine in fixed ratios, and they retain their individual chemical and physical properties.
D. The atoms retain their individual chemical properties, and they can only be separated from each other by a chemical change.

c no option is the correct one

A chemical compound can be described as substance composed of atoms from more than one element held together by chemical bonds in a fixed stoichiometric proportion. A compound has different physical and chemical properties from its constituent elements.

For example : compound water is made up of H and O bonded together and it has different properties from O and H.

Thus, among the given options, the one coreectly describing a compound is

a) The atoms are bonded together, and the compound has different physical and chemical properties than the individual elements.

c. heat could easily travel through the molecules in the air and escape/enter the flask. removing the air slows down the heat transfer.