Distinct points A, B, C, and D lie on a line, with A B=B C=C D=1. Points E and F lie on a second line, parallel to the first, with E F=1. A triangle with positive area has three of the six points as its vertices. How many possible values are there for the area of the triangle?
Answer Choices
A. 3
B. 4
C. 5
D. 6
E. 7