Final answer:
Celine should use carousel ads because they allow multiple images in one ad unit, enabling her to feature various cameras and engage with potential customers. Option a is correct.
Step-by-step explanation:
If Celine is a camera retailer looking to create engaging ads with images of products from her catalogue, the ad type she should use is carousel ads. Carousel ads allow retailers to showcase multiple images within a single ad unit, letting users swipe through various products or different aspects of a single product.
This format is highly visual and interactive, which can help Celine display her cameras in a compelling way and attract potential customers. On the other hand, collection ads might be used to showcase a group of related products, single image ads are for a more focused message with one product, and slideshow ads can provide an engaging video-like experience using multiple still images.