2. Dolphins communicate with one another in different ways. They make a great variety of sounds using high-pitched clicking sounds and whistles. The slightly different vocal pitch makes them understand which dolphin is speaking. Another way of communication is that they make physical contact with one another. In addition, they also communicate by using body language. Body language can be used to inform other dolphins about a nearby predator and where to find food.
The main idea of the paragraph is that ____________________.
a. dolphins make physical contact with one another
b. dolphins communicate by using body language
c. dolphins can communicate among themselves
d. dolphins make a great variety of sounds