Which of the following is a suspension?

• A. Flour in water
• B. Milk
• C. Salt in water
• D. Sugar water

Answer: (A)

This question tests the ability to tell apart suspensions, colloids, and true solutions. In a suspension, the solid particles are large enough that they do not dissolve in the liquid and will eventually settle out under gravity, making the mixture visibly heterogeneous and separable by filtration or settling.

Flour in water fits this description because flour doesn’t dissolve; the grains remain dispersed for a while but will settle to the bottom if the mixture sits, and you can separate them by filtration. Milk, by contrast, is a colloid: tiny fat droplets and proteins stay dispersed and give a cloudy appearance, but they don’t settle quickly and aren’t removed by simple filtration. Salt in water and sugar in water are true solutions: both solutes dissolve completely, producing a uniform mixture at the molecular level with no settling over time.