Answer: Option C
:
C
Let R denotes the relation ‘is brother of ‘.  Let X $ϵ$ A.  If x is a girl, then we cannot say that x is brother of x.
$\therefore$ (x,x) $\text{/}ϵ$ R    $\therefore$ R is not reflexive.
Let (x, y)    $ϵ$ R                   $\therefore$ x is a brother of y.
$\therefore$ y may or may not be a boy.
$\therefore$ we cannot say that (y, x) $ϵ$ R.
$\therefore$ R is not symmetric.
Let (x, y) $ϵ$ and (y, z)  $ϵ$ R.
$\therefore$ x is a brother of y and y is a brother of z
$\Rightarrow$ is brother of z $\Rightarrow$ (x, z)  $ϵ$ R
$\therefore$ R is transitive.
$\therefore$ The correct answer is (c).