答案：E

解析：

First let x equal the first value from Column X, that is, x=1. Then add 1 to each of the three values of y in Column Y as follows: 1 + 4 = 5, 1 +5 = 6, and 1 +6 = 7. Repeat this process for x=2, for which the possible values of x + y are 6, 7, and 8; and repeat it again for x=3, for which the possible values of x + y are 7, 8, and 9. If you compare these nine values, you see that 5, 6, 7, 8, and 9 are the only different possible values of the sums x plus y; therefore, there are five different values possible for x + y.