Drag and drop and hotspot question background:
47:30 aspect ratio
Single choice image question:
Thumbnail - 260x260 px (1:1 aspect ratio)
Image layouts (width):
One image: 900x545 px (1.65:1 ratio)
Image on the left/right /two images: 900x545 px / 250x152 px (1.64:1 ratio)
Three images: 900x545 px / 148x89 px (1.66:1 ratio)
Flip card:
Image only - 701x701 px (1:1 aspect ratio)
Image + text - 499x346 px (1.44:1 aspect ratio)
NOTE: in the above images, you can adjust the size and crop or extend the image in the image editor so the size can be any.
Section icon:
182х200 px (0.91:1 aspect ratio)
Course logo:
700x250 px, depending on the logo shape.
Background:
Cover background image - 768x1024 px (3:4 ratio).