Choose the odd one out and state the category to which others belong :

Dear student,
Please find below the answer:

a. Neuron is the odd one out. Others are all parts of the excretory system.
b. Excess sodium chloride. Others are all types of waste products produced by different organisms.
c. Hilum is the odd one out. Others are all parts of the nephron.
d. Papilla is the odd one out. Others all form a part of nephron.

Hope this clears your doubt.
Regards.