"Pick the most unsafe environment", followed by pictures of a house, a park, a volcano, a bed.
if you're a spammer is to choose randomly and make four times as many attempts. Which is why catchpas make you type six or more letters giving millions of combinations so you can't do it randomly. To get up to a similar resistance to random attempts with 'pick the unsafe environment' type questions you'd need of the order or eight of them (giving 4^8 or approx 65k combinations). Would you as a user want to fill in 8 of those things?
Watson played a simplified version of Jeopardy with no video or audio questions. This was a key compromise to allow a text based system to compete with humans. The AI problem of recognizing pictures is practically unsolved. It took Google's best researchers, a massive database of cat pictures, and a supercomputer just to train a computer to recognize when a cat was in a photo. So your sense of Watson's present abilities is a little skewed and unrealistic.
* "home and safe" "safe as houses" etc
* "safe in bed" "safely tucked up in bed" etc
* "volcano" ... no clear data. Certainly dangerous being a volcanologist, but that'd be great AI googlefu
* "pensioner attacked in park" .. "our parks are not safe" etc... Hmm, Parks are the most dangerous.
Because frequency of local newspaper reports is a bad measure for volcanos I guess.
My sense is that IBM's Watson could tackle this particular question. Also interesting to note that the question introduces external considerations, such as whether or not there's someone dangerous near the house, bed, park, etc. A human respondent will have to ignore the matter of whether there's additional context and second-guess the captcha author to get the problem right -- presumably the most unsafe environment is the volcano.