Final answer:
If you wanted to display a variant image on the cart page, rather than a product's default image, you would use the variant_img_url filter.
Therefore, the correct answer is: option D). variant_img_url
Step-by-step explanation:
Image variants are user-defined versions of page attachments. You can define each image variant differently so that you have images for various scenarios.
In this question, the variant_img_url is specifically designed to retrieve the image associated with a particular variant of a product.
For example, if a t-shirt comes in multiple colors, and the customer selects a blue variant, using the variant_img_url filter could ensure that the image of the blue t-shirt is displayed in the cart, enhancing the user experience by clearly confirming what they have selected.
Another example of image variants, you can create image variant definitions for different browser viewports or for various devices such as mobile phones, tablets, desktops, etc.