Which are the possible side lengths of a triangle

a. 3 cm, 5 cm, 9 cm
b. 4 cm, 8 cm, 10 cm
c. 6 cm, 9 cm, 17 cm
d. 8 cm, 10 cm, 18 cm

Possible side lengths of a triangle are determined by the triangle inequality:
a+b>c
where a and b are the shorter sides, (i.e. c is the longest side).
Note that equality does not hold, because it will make a "triangle" with an angle equal to zero degrees.

An example, choice a, 3+5<9, so they are not possible side lengths.

EDITED 2018-02-26
As already indicated in comments, (4, 8, 10) is a feasible set of sides for triangles because the shorter sides are 4 and 8, and the sum (12) is greater than the third side (10).