To determine where the function $f(x)$ is decreasing, we need to look at the intervals in which the slope of the curve is negative, meaning the function moves down as we move from left to right.

Analysis of Intervals

Observing the graph:

1. From point $A$ to point $B$, the function is increasing (the slope is positive).
2. From point $B$ to point $D$, the function is decreasing (the slope is negative).
3. From point $D$ to point $E$, the function is increasing again.

Therefore, the function is decreasing in the interval between points B and D.

Answer

The correct option is:

• C and D

Would you like further details or have any questions about this?

Related Questions:

1. How do we determine if a function is increasing or decreasing from a graph?
2. What role does the derivative play in identifying intervals of increase or decrease?
3. How can we identify relative maxima and minima points on a graph?
4. How does concavity affect the intervals of increase and decrease?
5. How do we interpret points where the function’s slope is zero?

Tip:

A function decreases where the slope (or derivative) is negative, and it increases where the slope is positive.