Final answer:
To make a background image fit the screen in CSS, use the 'background-size' property with either 'cover' to fill the element area or 'contain' to ensure the image is fully visible.
Step-by-step explanation:
To make a background image fit the screen in CSS, you can use the background-size property. You have several options, such as using values like cover, contain, or setting a specific width and height. The cover value ensures that the background image covers the entire background of the element, while contain ensures that the image is fully visible in the element, possibly leaving some empty space if the aspect ratio doesn't match. Explicit dimensions can also be set, though this is less responsive.
To cover the whole screen:
background-size: cover;
To ensure the image is fully visible:
background-size: contain;