A city grid of Anytown, USA is shown on the grid below. The fire department is represented by quadrilateral RSTU. Another fire department is opening in a different part of the city to maximize fire protection. The size of the new department's property must be congruent to the older department. Vertices A and B are plotted on the grid below to represent two vertices of the new fire department quadrilateral ABCD:
 What could be the ordered pairs representing vertices C and D of quadrilateral ABCD so that the new fire department is congruent to the old fire department?
 a. C(1,1) , D (4,1) 
 b. C (1,6) , D (4,6) 
 c. C (1,2) , D (4,2) 
 d. C (1,4) , D (4,4)