The trick is to pretend you're an idiot. If the bicycle and the person on it map mostly to a rectangle of 8 squares, most people will be so stupid or hasty that they'll click that, nevermind that a human is not part of the bicycle.

The same is true with, say, buses. See an image of a delivery van? Bus! It asks you select all cars and you see no car but a vague pixel blob that someone stupid would identify as a car? Car!

One of the few things that this doesn't work with is stairs, because the side of stairs being stairs or not is something apparently no one can agree on.

Answer how you'd want a Waymo to react

If it can go either way then you can pass the captcha either way too. There isn't a single correct answer to these captchas.

The 'Process Turing Test' extends the CAPTCHA from 'What would a reasonable person click' to 'How would a reasonable person click'.

For example, hesitation/confusion patterns in CAPTCHAs are different between humans and bots and those can actually be used to validate humans