Records from 1850 to 1900 show that in a certain region, babies' birth weights each year varied with the success of t...

Can someone explain how “other” doesn’t make A incorrect? There are only two phenomena mentioned, brith weight and crop yield. Answer A is saying it uses the correlation between Theo phenomena and applies to to two “other” phenomena. I eliminated this answer based on that word. I still don’t see how it can be correct.