Finish the following sentence with the best choice: how to find the perimeter of a trapezoid

Choices:
- Perimeter = add lengths of all sides    P = a + b1 + b2 + c x b1
- Perimeter = add lengths of all sides    P = a + b1 + b2 + c

Answer:
Perimeter = add lengths of all sides    P = a + b1 + b2 + c