Answer: Option (a) is the correct answer.
Explanation:
An element is defined as the substance which cannot be broken down into simpler substances.
For example, a piece of sodium metal will contain only atoms of sodium.
Whereas a compound is a substance that contains atoms different elements which are chemically combined together in a fixed ratio by mass.
For example, sodium chloride and water () are both compounds as they both of them contain different atoms which are chemically combined.
Thus, we can conclude that 200 milliliters of water combined with sodium chloride is a mixture of two compounds.