A non-linear trend occurs when the rate of change is not constant. Option B describes a variable increasing at a decreasing rate, which means the rate of increase is changing over time, making it non-linear.

Explanation:

• Option A (Incorrect): Constant rate of increase represents a linear trend.
• Option B (Correct): Decreasing rate of increase means the slope is changing, indicating a non-linear relationship.
• Option C (Incorrect): Discrete intervals don't necessarily imply non-linearity; a variable can increase at discrete intervals but still follow a linear pattern.
• Option D (Incorrect): A negative regression slope still represents a linear relationship, just with a negative constant rate of change.

Non-linear trends are characterized by changing rates of change, which can be visualized as curved patterns rather than straight lines in graphical representations.