[tex]\frac{a}{b}=\frac{d}{c}[/tex]
1) Let's sketch this out to better grasp it:
2) According to the Triangle Proportionality Theorem, two segments are considered proportional ones, following this ratio:
[tex]\frac{a}{b}=\frac{d}{c}[/tex]
Because the line divides the triangle into proportional segments.
3) Hence, the answer is B
