Possible answers: (1). An infection. (2). amoebae. (3). heating liquids. (4). An antibiotic. (5). smoking. (6). Vitamins. (7). prolactin release. (8). Food poisoning.

You are presented with the quiz "What causes edema?" But you don't know the answer, so you turn to your teacher to ask for hints. He says that "infection can cause bodily tissues to swell" and "doctors call such tissue swelling edema". So, what's the best answer to the question?
Answer:
(1).