4.If maples are planted, the side of the street that has four trees must have
(A)red oaks in positions 1 and 7
(B)red oaks in positions 3 and 5
(C)sycamores in positions 1 and 3
(D)sycamores in positions 1 and 7
(E)sycamores in positions 3 and 5
答案：EB AE