By looking at the scatter plot in the image, we can see that the data points follow a downward curving trend that flattens out as $x$ increases. This behavior is characteristic of an exponential decay pattern, where the data decreases rapidly at first and then levels off.

Hence, the best-fitting regression model for this data would be:

D. Exponential

Would you like to know more details about regression models or ask any questions?

Here are 5 related questions you might find useful:

1. What is the difference between exponential and linear regression models?
2. How do you determine the equation of an exponential regression model?
3. What are some real-world examples where exponential decay is observed?
4. How is a regression model different from a curve fitting technique?
5. Can we use polynomial regression to fit this data? If so, how would it differ?

Tip: When identifying regression types visually, always look for the trend of the data over both small and large values of $x$.