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