Which of the following can be the side lengths of a triangle?

A:12,9,21

B:7,6,12

C:3,8,14

D:23,13,37

In a triangle the sum of two sides is always greater than the third side.

A:12,9,21

12+9 = 21

21 = 21 ⇒ no

B:7,6,12

7+6 = 13

13 > 12 ⇒ yes

C:3,8,14

3+8 = 11

11 < 14 ⇒ no

D:23,13,37

23+13 = 36

36 < 37 ⇒ no

Answer: B:7,6,12