2.d (After drawing a straight line, one angle is equal and the other angle is equal, so the angles can be almost the same)

3.c (multiply by k and let it go, then do it slowly. Not excluding a+b+c)

4.B(30 corresponds to 50 and 60 respectively)

5.a (this is ok for the time being, or let the length of 1/width = width/ half of the width be the second root sign)

Question 6 is wrong. There is no right angle.