Official Solution:If \(ABCD\) is a quadrilateral, is \(AB = BC = CD = DA\)? (1) AC is perpendicular to BD.
This statement implies that the diagonals are perpendicular to each other. In this case, \(ABCD\) could be a kite (answer NO), a rhombus (answer YES), or a square, which is a special type of rhombus (answer YES). Not sufficient.
(2) \(AB+CD=BC+DA\).
This statement implies that the sum of opposite sides is equal. Not sufficient.
(1)+(2) Combining the two statements, \(ABCD\) could be a kite (see the diagram below) - answer NO, or a square/rhombus - answer YES. Not sufficient.
Answer: E