Try this exercise. Fill in the missing part by typing it in.

When optimizing images for responsive web design, it's important to reduce their file size without sacrificing quality. This can be achieved by using techniques such as compression, resizing, and lazy loading. One way to specify different image sizes is by using the srcset attribute, which allows the browser to choose the most appropriate image based on the device's screen size. Another technique is ____, which delays the loading of images until they are needed. This significantly improves page load times, especially for pages with many images.