How many types of introns are there?
Length four Many SO2 three CO 2 small genus
A B C D E F G H
Protein There are many types of protein.
There are many types of introns. 
How many types of introns are there? (A) Length (B) four (C) Many (D) SO2 (E) three (F) CO 2 (G) small (H) genus