Check the notes on Wikipedia. The source for China is from 2022, and the Indian source (from March 2023) claims that India will surpass China by April... Which has, of course, transpired.
Worldometer lists India as most populated directly: https://www.worldometers.info/world-population/population-by-country/
It broke the news a couple of months ago that India is now the world's most populous nation, all sorts of papers were writing about it... But I suppose you're right in the end, I ought to replace it with something upon which there is more consensus.
One of those pictures is taken in Taiwan(Republic of China). Maybe the question can be changed as "which picture is taken in PRC" or just remove that Taiwan picture. Whether Republic of China is China is still disputed.
Whether the Republic of China (Taiwan) is China is not disputed by anybody until either party changes its stance. Taiwan is under a different government but no relevant authority on the island claims it to not be China. But you are right that the question can be confusing. I'll consider changing it later.
Great quiz!
Worldometer lists India as most populated directly: https://www.worldometers.info/world-population/population-by-country/