What does the term "miscible" refer to?

The term "miscible" specifically refers to the ability of two liquids to mix together in all proportions without separating into different layers. This means that when miscible liquids are combined, they form a homogeneous solution. A common example of miscible liquids is water and ethanol; they can be mixed in any ratio, and the resulting mixture will have consistent properties throughout.

In contrast, the other options describe different scenarios for substances. The option referring to liquids that cannot mix describes immiscible liquids, which will separate into two distinct layers (like oil and water). The option about solid substances that dissolve in water pertains to solubility rather than miscibility, and gases that combine under pressure relates to gas behavior, which does not align with the definition of miscibility as it pertains only to liquid interactions.