Which must be a mixture of substances?
1. solid
2. liquid
3. gas
4. solution

the one that must be a mixture of substance is : 4. Solution here are some examples that proof option 1 - 3 could consist only with a single substance : Solid = Fe ( most commonly known as iron) Gas = He ( Most commonly known as helium) Liquid = Hg (most commonly known as mercury)

4. Solution

Further explanation

Mixtures are materials composed of two or more kinds of substances that still possess their original properties. Mixtures can also be said to represent a combination of several substances, elements or compounds

There are two types of mixtures, i.e., homogeneous mixture (or solution) and heterogeneous mixture.

Homogeneous mixture: mixture which each part contains a similar amount of solute, for example, vinegar acid solution, sugar solution, and salt solution.Heterogeneous mixes: mixtures of which each part contains an unequal amount of solute, for example, river water, sewage water, and coffee drinks.

The solution is a homogeneous mixture of two or more substances that dissolve one another and each of the constituent substances cannot be distinguished physically anymore.

The solution consists of two components, i.e., solute and solvent.For example, a salt solution consists of salt as a solute and water as a solvent.

In chemistry, we already know the phase of matter or state of matter, i.e., solid (s), liquid (l), gas (g), and aqueous (aq). Every chemical solution in a reaction is labeled as an aqueous phase, e.g, as a salt solution.

Consider the following examples:

as a solid metal iron, an element. as liquid water. as ice solids. as water vapor with a gaseous phase. are compounds of the same chemical formula but different phases.Learn moreAbout the mass and density of substances  linkCalculating the pH value of weak base linkHow was the water filtered to remove debris and living organisms?  link

Keywords: which must be, a mixture of substances, solid, liquid, gas, solution, homogeneous, heterogeneous, phase of matter, state, aqueous, salt, water

False because saturated fatty acids contain only single bond

500bc indiais the answer.