Final answer:
The Iris Blur effect simulates a shallow depth-of-field by selectively blurring the background to draw attention to the in-focus subject.
Step-by-step explanation:
The effect that simulates a shallow depth-of-field is d. Iris Blur. In image editing software, an Iris Blur effect is often used to mimic the type of blurring that one might see in a photograph taken with a shallow depth of field. This is typically achieved by selectively blurring the background while keeping the subject in focus, thereby drawing attention to the subject. Feathering and Soft Edge Blur can also produce somewhat similar effects but are more uniform and less precise than Iris Blur. The Gaussian Blur effect applies a uniform blur over the entire image and does not simulate shallow depth-of-field.