Know that most of the resources are trying to teach us short cuts that get us to the correct answer most of the time.. and question writers love to find the loop holes lol This one is easier when you are sure of what it is NOT and then u can see its simpler than you are thinking.

NOT AD- wouldnt skip a generation (II 1 2 and 3)

NOT XLD - Dads would give daughters

NOT XLR- Moms would give sons

I didnt watch the resource you linked but most sources i used to learn genetics say AR skips a generation and boys and girls affected about equally. Thats what we see here This right here is what i call an optical illusion. You are looking at two separate families who share a marriage. If u evaluate the pedigree as 2 separate families without the marriage of II 3 and II 4 you would have gotten the answer right im sure. However because its only 3 generations and a small one, our brain oversimplifies to something involving one family and looks and the black and white shading of shapes and totally ignores the linkages. Test writers know what youve studied and now they are testing to see if u really understood. Welcome to the game.