If abcd is a parallelogram which of the following statements is not true

A+C = 180 (first answer choice)

This statement is only true if and only if we are dealing with a rectangle (where all four angles are 90 degrees). Otherwise, the statement is false.

side notes:

The second statement that AN = NC and DN = NB is true because a parallelogram has its diagonals bisect each other. In other words, the diagonals cut in each other in half.

The third statement that AD = BC and DC = AB is true because opposite sides of a parallelogram are parallel and congruent.

The fourth statement is true because opposite angles of a parallelogram are congruent. If A = C = 90, then A+C = 90+90 = 180 backing up the claim I made earlier, but it's possible that A and C are non-right angles making this parallelogram non-rectangular.