Question

What are the possible side lengths of a triangle

Answer 1

NONE of those lengths will form a triangle.
Basically, the longest side of a triangle must be less than the sum of the other 2 sides.  In this case NONE of those choices will form a triangle.

Answer 2

Hey!
So to find this you have to add the 2 smaller lengths and see if they are larger than the largest length. 
3 + 5 is 8 and that is not greater than 9 so A is wrong
4 + 8 is 12 and it is larger than 10, so maybe...
6 + 9 is 15 and that is not larger than 17 so that is out
8+10 is 18 and that is equal to but not larger than 18 so that is out
Your answer is B!
Hope this helps!