Predict the answer first, then click the link and check the Network tab. Clear the list with the 🚫 button before each one so it is easy to count.
1. It is HTML only — no images, no external stylesheet.
4. The HTML, then one request for each of the three pictures.
One image (HTML + a picture) and An external stylesheet (HTML + a CSS file). A big image and Things that go wrong also make 2 — so really there are four.
The HTML plus one image. The <details> boxes and all the
styling are built into the HTML file, so revealing an answer costs nothing:
click one and watch — no new row appears, because nothing new is fetched.
Usually yes, but they are cheap. It may serve files straight from the cache (Size says disk cache), or ask the server and get 304 Not Modified back. See cached images.