1. For integers $a, b, c$ and $d$, it is given that the difference between $a$ and $b$ is 2, the difference between $b$ and $c$ is 3, and the difference between $c$ and $d$ is 4.

Which of the following values cannot be the difference between $a$ and $d$?
A) 1
B) 3
C) 5
D) 7
E) 9