Diagonal cross section through widest part of a sphere

Which statement is not always true for a parallelogram? (a) opposite sides are congruent. (b) diagonals bisect each other. (c) it has 4 congruent angles. (d) consecutive angles are supplementary.

Rhombus adef is inscribed into a triangle abc so that they share angle a and the vertex e lies on the side bc . what is the length of the side of the rhombus if ab=c, and ac=b.

Willard f. libby received his undergraduate degree from . after he completed his graduate work, he became a professor at . in 1960, he won a nobel prize in .