The amount of matter in an object is its mass. Mass is a measure of the amount of material in an object. It is commonly measured in units such as grams or kilograms. The other options provided in the question do not represent the amount of matter in an object:
1. Charge (OA) is a property of matter related to the presence of protons and electrons, which determines how they interact with each other.
2. Volume (OC) is the amount of space that an object occupies. It is a measure of the physical size of an object, not the amount of matter it contains.
3. Density (D) is the mass of an object per unit volume. While density is related to the amount of matter in an object, it is not the same as the mass itself.
Therefore, in this context, the correct answer to the question is option B: mass.
