∠ D = 80°
Step-by-step explanation:
Δ BCA and Δ DCE are congruent ( SAS postulate )
Thus corresponding angles are congruent, thus
∠ D = ∠ B
The sum of the 3 angles in a triangle = 180°
Subtract the sum of the 2 angles in Δ ABC from 180° to find ∠ B
∠ B = 180° - (30 + 70)° = 180° - 100° = 80°, then
∠ D = 80°
Answer is B. Hope this helps. :-)