Amongst the following statements, that which was not proposed by Dalton was:

First, let us recall Dalton’s atomic theory (1808). Dalton proposed that:

$$1.$$ Matter is made up of tiny, indivisible particles called atoms.
$$2.$$ All atoms of a given element are identical in mass and all other properties, while atoms of different elements have different masses and properties.
$$3.$$ Atoms are indestructible and conserve their identity in every ordinary chemical change; during a chemical reaction atoms are merely rearranged.
$$4.$$ Compounds are formed when atoms of different elements combine in simple whole-number ratios.

Now we compare each option with the above list.

Option A states that “chemical reactions involve reorganization of atoms which are neither created nor destroyed.”
This is exactly Dalton’s third postulate. So Option A was proposed by Dalton.

Option B says “all the atoms of a given element have identical properties including identical mass, whereas atoms of different elements differ in mass.”
This matches Dalton’s second postulate. Hence Option B was also proposed by Dalton.

Option C states “when gases combine or are produced in a chemical reaction they do so in a simple ratio by volume, provided all gases are at the same temperature and pressure.”
This statement is known as Gay-Lussac’s law of combining volumes, formulated in 1808-1809 after Dalton had already announced his atomic theory. Dalton did not include any reference to volumes of gases in his postulates. Therefore Option C was not proposed by Dalton.

Option D says “matter consists of indivisible atoms.”
This is identical to Dalton’s first postulate, so Option D was indeed proposed by Dalton.

Comparing all the options, only Option C is outside the scope of Dalton’s original atomic theory.

Hence, the correct answer is Option C.