Otitis Media Can Occur with or Without an Effusion

Otitis media can occur with or without an effusion. Which of the following best describes an effusion?

A) accumulation of fluid such as in the middle ear or pleural cavity
B) movement of fluid back and forth between the outer ear and inner ear
C) a blocked eustachian tube causes pressure in the middle ear
D) escape of fluid from the middle ear into surrounding tissues