The first question is c; Move one diagonal parallel to make it pass through the other vertex, and the side length of the triangle formed by it and the other diagonal is twice as long as that of the two diagonals and the parallelogram, respectively, then the problem becomes whether a triangle can be formed. The condition for the existence of a triangle is that the sum of any two sides is greater than the third side, and the difference between the two sides is less than the third side. Now the side with twice the length of the parallelogram is taken as the third side, and its length is 14 * 2 = 20.

The seventh question 1 15, the sum of the internal angles of the quadrilateral is equal to 360, and there are already two right angles. The diplomatic angle is 65, so the included angle between the two heights is 360-90-90-65= 1 15.

Question 8: 23cm, the problem should be the perimeter of the triangle DEF, but the EF can't be found. There are too many such situations. The perimeter of the triangle DEF is 23cm, because each side of it is one side of the original triangle ABC, so the perimeter is half that of the triangle ABC, 46/2=23.

Question 9: 5cm

The eleventh question is112 or1/6; E is one third of BC, maybe a little to the left or a little to the right, so there are two situations. The ratio of △BEF to △ABE can be obtained by triangle similarity. The height of △BEF is half that of △ABE, and the bottom may be one-third or two-thirds, so the area of △BEF is one-sixth or one-third of that of △ABE, and then the area of quadrilateral is twice that of △ABE, so △BEF is quadrilateral 1/65438.