Observe the graph:
It is a parabola.
Cosider option (d) equation is .
Compare with .
.
Since, the equation represents a parabola.
Option (d) is correct.
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=e27486e350d88040b5bcd48ff85ca318.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=49dbfc4d28c13772a9dcf547327a429c.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=98380f694531d5fa18bc32ed674d47e3.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=6b8c5dd5536710631e3e16c641d875e7.png\")
the equation represents a parabola.