Final answer:
b. suspension.The answer is a suspension, which is a type of liquid dosage form characterized by large particles that are not fully dissolved and can settle over time, hence requiring the instruction to 'shake well' before use.
Step-by-step explanation:
The correct answer is a suspension. A suspension is a liquid dosage form where the solute is not dissolved but is distributed throughout the solvent. The particles in a suspension are relatively large, and due to their size, they may settle over time, which is why it is essential to shake well before use to redistribute the particles evenly.
An example of a suspension is a mixture of mud and water, where after mixing, the particles are suspended temporarily, but once settled, the solids gather at the bottom of the container.
Unlike suspensions, a solution is a homogeneous mixture where the solute is fully dissolved in the solvent. In solutions, the dissolved particles are molecules or ions that do not settle out. Between these two lies a colloid, where the particles are larger than those in a solution but are small enough to remain evenly dispersed and not to settle on standing, exhibiting the Tyndall effect.