Observe the graph:
It is an ellipse.
Cosider option (b) equation is .
Compare with .
.
Since, the equation represents an ellipse.
Option (b) is correct.
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=9b23a5711a4b5727bb7d445c26e6c4b2.png\")
..![\"\"](\"http://www.mathskey.com/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=4e0c35a3395f9e0fc7855b2b2ff789ee.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=bcbf6fe314f9c379e2a6a4d5dc2fcb68.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c1cca837556914e9dafb3518cb3e64a1.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=eab01704892b64c1dbf9114733073add.png\")
the equation represents an ellipse.