An inflammation of the middle ear is called

Otitis media

Explanation:

Otitis media is the inflammation which located in middle ear. It occur as a result of sore throat, cold, or respiratory infection.

Middle ear infections occur because of malfunction of eustachian tube. It is a canal which links middle ear with throat area. The tube helps to equalize pressure between outer ear and middle ear. When eustachian tube does not working properly, it prevents the normal drainage of the fluid from  middle ear which cause build up of fluid behind eardrum which further allows for growth of the bacteria and the viruses in ear which can lead to otitis media.

Different types of otitis media include following:

that is wrong, its not thymus.

i believe your answer would be c.. : )