Question

which choice shows three lengths that cannot be the lengths of the three sides of a triangle

Answer 1

For triangles Sum of any Two sides should be always more than the length of the Third side.
A) 2cm,8cm,8cm 
8+8=16 >2 True
8+2=10 >8, True
8+2=10 >8, True
B) 2cm,3cm,6cm
2+3=5 > 6 False.  It is impossible in a triangle.
3+6=9 > 2 True
2+6=8 >3 True

The answer is B.