Fact 1: Fish have a circulatory system with a two-chambered heart.

Fact 2: Mammals have a four-chambered heart.

Given the two facts above, answer the question "How many sections does a fish heart have?" with the following options: 
- ovum
 - fat
 - four
 - p53
 - two
 - cut
 - bone
 - stem


 

     two    