5. Given a quadrilateral $A B C D$ with a point $E$ inside it, connecting $A E, B E, C E, D E$ divides the quadrilateral $A B C D$ into four triangles of equal area. Then the proposition
甲、 $A B C D$ is a convex quadrilateral;
乙、 $E$ is the midpoint of diagonal $A C$ or diagonal $B D$;

丙、 $A B C D$ is a parallelogram
(A) Only 甲 is correct;
(B) Only 乙 is correct;
(C) 甲, 乙, 丙 are all correct;
(D) 甲, 乙, 丙 are all incorrect.
$5 .(B)$;