There is a theorem that states the the sum of the smaller sides must be higher than the highest side
a) 2, 4, 5
2 + 4 > 5 this is a triangle obtuse
b) 3, 4, 5
3 + 4 > 5 this is a triangle right
c) 6 , 7 , 8
6 + 7 > 8 this is a triangle Acute
d) 3, 3, 10
3 + 3 < 8 this is not a triangle Cannot form a triangle