I guess this task is somewhat similar to MC.
1. Each word should have aria-selected.
2. The whole task should have aria-multiselectable and aria-labelledby.
3. You should be able to use the arrows to navigate between options.
4. The task should have more appropriate roles than "button". Roles listbox and option seems like a good fit, but that should be double checked.
You should be able to easily explore and use mark the words questions without looking at your computer monitor.