Is Uworld harder than USMLE?

The big key here is that this young boy has been dizzy for an hour. Dizziness can be caused by a variety of things, but in this chain of choices, the most likely one is the O2 portion of the electron chain, or answer E. As a fellow headache sufferer, I know this can happen. A headache can knock you on your feet if you’re not careful.

For headaches that you can’t get rid of, dizziness can set in. It can make it hard to do anything, but dizziness can often be caused by lack of oxygen. This young boy’s other symptoms - nausea, vomiting, etc. - can also be attributed to the dizziness, but it may not be the cause for this young boy.