What is the biggest thing a blue whale can swallow?

http://proxyponder.com/2014/09/blue-whales-population-rebounding/

A. A very large mushroom? No!
B. A small family car? No!
C. A sailor? No!
D. A grapefruit? Yes!

Quite interestingly, a blue whale’s throat is almost exactly the diameter as its belly button, which is about the size of a side plate.

Their diet consists of tiny pink, shrimp-like crustaceans called “krill”. The narrow gauge of a blue whale’s throat means it couldn't swallow big living and non-living things. The only whale with a throat wide enough to swallow a person whole is the sperm whale.

Reference:

Lloyd, J., & Mitchinson, J. (2006). The book of general ignorance. New York: Harmony Books.

 GeographyBlog. (n.d.). Retrieved May 6, 2015, from http://geog-ashu.blogspot.com/2010/04/driest-place-on-earth.html