It's a shame!!

It's a shame to miss a question on insects since I'm taking Entomology RIGHT NOW:(
To show my apology to Dr. Stoffer, I would like to go over the question on malpighian tubules.

It was basically asking the organ of earthworm which has the same function as malpighian tubules of grasshopper.
First of all, we need to know what malpighian tubules are.
According to mondofacto, online medical dictionary, Malpighian tubules is "One of the tubular or hairlike excretory organs arising from the midgut-hindgut junction of many arthropods. Two to several hundred such tubules may be present. They collect waste from the body fluids and discharge them into the hindgut."
Here's some pictures...













So basically malpighian tubules are kidney-like organ, I can say. Now, we need to figure out what is the correct answer!
We had some possible answers; gizzard, crop, nephridia, esophagus, and ganglia.
At first sight, we can eliminate ganglia, because it is just a mass of nerve tissue and has no relation with excretory system. Esophagus can be also eliminated since it is just a tube which food passes.
Then which of these three answers is correct? Let's check all the definitions.

Gizzard: The second, or true, muscular stomach of birds, in which the food is crushed and ground, after being softened in the glandular stomach (crop), or lower part of the oesophagus; the gigerium.

Crop (obviously not the agricultural "crop"!): A crop (or croup) is a thin-walled expanded portion of the alimentary tract used for the storage of food prior to digestion that is found in many animals, including gastropods, earthworms, leeches, insects, and birds.

Nephridia: A segmental tubule; one of the tubules of the primitive urinogenital organs; a segmental organ.

Which is the closest to kidney? Yes, the answer is Nephridia.
Basically, this kind of question cannot be solved without knowledge, so I wanted to get a chance to educate myself. Hope this post will help you in the future at some point!