Answer:
B
Explanation:
Since the triangle is isosceles the base angles are equal
One base angle is given as 70°, thus the other base angle is also 70°
The sum of the 3 angles in a triangle = 180°
Subtract the sum of the base angles from 180 for third angle
third angle = 180° - (70 + 70)° = 180° - 140° = 40° → B