Final answer:
Salad is correctly identified as a heterogeneous mixture because its components are distinct and visible. Milk, river water, and beach sand, while sometimes appearing homogeneous, are typically heterogeneous on a closer examination due to the various particles and substances present. So the correct option is A.
Step-by-step explanation:
The student has asked which substance is correctly identified as a homogeneous or heterogeneous mixture. First, let's understand the difference between the two:
- A homogeneous mixture, also known as a solution, has a uniform composition throughout. An example is saltwater where the salt is uniformly dissolved.
- A heterogeneous mixture has a non-uniform composition, where the different components can usually be seen. An example is salad, where you can see the lettuce, tomatoes, and other ingredients separately.
Now, let's address the student's options:
- Salad is correctly identified as a heterogeneous mixture because its components are clearly distinguishable.
- Milk is often referred to as a homogeneous mixture because it looks uniform throughout when you pour it, though on a microscopic level it can be heterogeneous due to fat droplets.
- River water is typically a heterogeneous mixture because it can contain sediment and varying particles.
- Beach sand is a heterogeneous mixture as it consists of various types of particles like shells, rocks, and minerals that can be seen.
Using the information given, we can infer that A. salad -- heterogeneous is the correctly identified option.