The correct option is B Isosceles
From Converse of Basic Proportionality theorem,
Since ADDB=AEEC
∴DE∥BC.
Given ∠ADE=∠ACB ---- (1)
Since corresponding angles in parallel lines are equal, we have
⇒∠ADE=∠ABC -----(2)
From (1) & (2),
⇒∠ABC=∠ACB
Hence it is an isosceles triangle.