Final answer:
An isosceles trapezoid has congruent base angles but does not have a midsegment and the same-side interior angles are supplementary, not complementary.
Step-by-step explanation:
An isosceles trapezoid is a trapezoid with two congruent base angles and congruent legs. Let's evaluate each statement:
I. It will have a midsegment: This statement is incorrect. An isosceles trapezoid does not have a midsegment. A midsegment is a line segment connecting the midpoints of the non-parallel sides of a trapezoid, and an isosceles trapezoid does not have non-parallel sides.
II. The base angles are congruent: This statement is correct. In an isosceles trapezoid, the base angles, which are the angles formed by the bases and the legs, are congruent.
III. The same-side interior angles are complementary: This statement is incorrect. The same-side interior angles of an isosceles trapezoid are supplementary, meaning they add up to 180 degrees, not complementary which adds up to 90 degrees.
Therefore, the correct answer is a. I and II only