Answer the following questions with the capital city. Remember: the superlative corresponds to the CAPITAL, not the country. For population, it refers to city proper!
This refers to city proper (I'll make a note about that), but I believe the answer isn't Beijing nor is it those listed. According to worldlibrary.org, the largest by city proper is Moscow. I'll fix that, along with some other problems.
For the highest in elevation, to avoid arguments about how La Paz is only the de facto capital of Bolivia, I added the next highest capital as a possible answer, as well as Sucre, because why not.