Define a binary relation R on a set A to be anti- reflexive if xRx doesn’t hold for any x 2 A. The number of symmetric, anti-reflexive binary relations on a set of ten elements is

Define a binary relation R on a set A to be anti- reflexive if xRx doe

1.	Define a binary relation R on a set A to be anti- reflexive if xRx doesn’t hold for any x 2 A. The number of symmetric, anti-reflexive binary relations on a set of ten elements is
A.	210
B.	250
C.	245
D.	290
Answer» D. 290