Answer: B. 15
Step-by-step explanation:
In the given picture, we have a right triangle having two sides other than hypotenuse (Side opposite to right angle).
The Pythagoras theorem of right triangle says that the square of longest sides is equal to the sum of the square of the other two sides.
For the given right triangle , we have
[tex]BC^2=AB^2+AC^2\\\\\Rightarrow BC^2=9^2+12^2\\\\\Rightarrow\ BC^2=81+144\\\\\Rightarrow\ BC^2=225\\\\\Rightarrow\ BC=\sqrt{225}=15[/tex]
Hence, the length of BC =15 units
