Joy has 30 thin rods, one each of every integer length from 1 cm through 30 cm. She places the rods with lengths 3 cm, 7 cm, and 15 cm on a table. She then wants to choose a fourth rod that she can put with these three to form a quadrilateral with positive area. How many of the remaining rods can she choose as the fourth rod?<spanclass=′latex−bold′>(A)</span>16<spanclass=′latex−bold′>(B)</span>17<spanclass=′latex−bold′>(C)</span>18<spanclass=′latex−bold′>(D)</span>19<spanclass=′latex−bold′>(E)</span>20