Two straight lines are parallel, and the internal dislocation angle is equal (the internal dislocation angle is equal, and the two straight lines are parallel).

Two straight lines are parallel and the isosceles angles are equal (the isosceles angles are equal and the two straight lines are parallel).

Two straight lines are parallel and complementary to the side inner angle (complementary to the side inner angle, two straight lines are parallel).

The three angles of an equilateral triangle are equal.

The line segment between two points is the shortest.

It should be right. . It's a little sad to see a satisfactory answer. .