The correct option is (e).

Remember that, in a triangle, the sum of any two sides must be greater than the third side. Since $1+5$ is not greater than 7, the third side cannot measure $1 \mathrm{~cm}$.
If two sides of a triangle measure 5 and 7 cm, then the third side cannot measure how many centimeters?
(a) 11
(b) 10
(c) 6
(d) 3
(e) 1