Given:
In triangle ABC,
AB=10
BC=5.
AC is the third side of triangle ABC.
If, a, b and c are lengths of three sides of a triangle, then the sum of any two sides of the triangle is greater than the third side of the triangle. Also, the difference between any two sides of the triangles is always less than the third side of the triangle. i.e.,
[tex]|a-b|
Since in triangle ABC, AB=10 and BC=5, then
[tex]\begin{gathered} |AB-BC|Therefore,
5 is the correct expression.Option C is correct.