Which of the following sets of numbers has the property that the sum of any two numbers in the set is also in the set? I. \(\{ 1,2,3,...\}\) II. \(\{ 1,3,5,...\}\) III. \(\{ 10,20,30,...\}\)
(A)I only (B)II only (C)III only (D)I and III only (E)II and III only
D