Pick from:
[1]. An infection
[2]. amoebae
[3]. heating liquids
[4]. An antibiotic
[5]. smoking
[6]. Vitamins
[7]. prolactin release
[8]. Food poisoning

Fact 1: Infection can cause bodily tissues to swell. Fact 2: Doctors call such tissue swelling edema. Given the two facts above, what causes edema?
Answer:
[1].