Among the options provided, the correct choice for a pure substance is c) sugar.
A pure substance is defined as a material that has a consistent composition and properties throughout. In this case:
- A) Iced tea: This is a mixture of tea, water, and possibly sugar or other flavorings. It does not have a uniform composition.
- B) A casserole: This dish consists of various ingredients, making it a heterogeneous mixture with different properties apart from one another.
- C) Sugar: This is a pure substance, specifically a compound, composed solely of sucrose molecules.
- D) Sugar water: This is a solution of sugar dissolved in water, which means it contains more than one component.
Thus, the only pure substance in the list is sugar, as it maintains consistent composition and does not change regardless of the sample taken.