To determine which curves indicate a function, we can apply the vertical line test. A curve represents a function if and only if no vertical line intersects the curve more than once. Let's analyze the curves:

• Curve A: This is a typical wave-like curve. A vertical line drawn at any point will intersect the curve exactly once. It passes the vertical line test, so Curve A is a function.

• Curve B: This appears to be a parabola, which also passes the vertical line test. Every vertical line intersects the curve only once. Therefore, Curve B is also a function.

• Curve C: This is a closed loop (a circle). A vertical line drawn through certain parts of the circle will intersect it in two places. It fails the vertical line test, so Curve C is not a function.

• Curve D: This curve resembles a sideways parabola or a loop. A vertical line through this curve will intersect it multiple times. It fails the vertical line test, so Curve D is not a function.

Thus, only Curves A and B represent functions.

The correct answer is: A and B.

Would you like further details or have any questions?

Here are some related questions you could explore:

1. What are examples of functions that pass the vertical line test?
2. How do horizontal lines affect determining whether a graph is a function?
3. Can a graph of a circle ever represent a function?
4. How does the vertical line test relate to one-to-one functions?
5. What is the difference between a relation and a function?

Tip: Always remember, a function maps every input (x-value) to a unique output (y-value).