ii, iii and iv.
So, option C is correct.
Above grammar is for equal no of x and y
from Non-terminal $S \rightarrow xB$
$\Rightarrow xy$ [as $B \rightarrow y$ one $y$ for one $x$]
$S \rightarrow xB$
$\Rightarrow xxBB$ [as $B \rightarrow yBB$ one $B$ result in one $y$ for one $x$ ]
$S \rightarrow xB$
$\Rightarrow xyS$ [as $B \rightarrow yS$ one $y$ for one $x$ and start again]
Note: Same applies for string start with $y$ i.e . $S \rightarrow yA$.