`stackrel(harr)(AB)` is perpendicular to `stackrel(harr)(CD)`. How many 90° angles are formed by the intersection?

(10 points) 1. cone 2. rectangle 3. triangle 4. circle 5. cylinder a. perpendicular cross section of a pyramid b. perpendicular cross section of a cylinder c. parallel cross section of a sphere d. shape created when a rectangle is rotated about the y-axis e. shape created when a right triangle is rotated about the y-axis