听力原文： Today we are going to talk about a species of fish that is rather unique: Today's lecture is about sea horses, if you've seen a sea horse, you may have noted that it has a horse-like head attached to its body. The sea horse has a long snout that is good for sucking. Instead of scales like most fish, sea horses have skin that is stretched over bony plates. The body extends to a prehensile tail, meaning that the tail can be used to grasp. The sea horse may grasp sea grass or coral to keep it stable in a moving current.
The sea horse has fins on its back that it can use to propel it through the water. However, sea horses aren't very good swimmers. They do not move quickly over great distances. The sea horse also has chest fins that it uses for stabilization. The chest fins help the sea horse float in an upright position.
One particularly unique feature of sea horse is that only the male becomes pregnant. The female inserts ripe eggs into the male' pouch, where they are fertilized. The eggs become embedded in the pouch wall.
What is this lecture mainly about？

A. Usual Species of fish.
B. Characteristics of a unique sea animal.
C. The harvest of fish eggs.
D. Unusual species of horses.