给h1标题添加背景图片( bg.gif),并让其沿X轴平铺,如下哪个代码正确?
A.
h1{ background-image:url(bg.gif); background-repeat:no-repeat; background-position: middle center;}
B.
h1{ background-image:url(bg.gif); background-repeat:no-repeat; background-position: center middle;}
C.
h1{ background-image:url(bg.gif); background-repeat:no-repeat; background-position: center center;}
D.
h1{ background-image:url(bg.gif); background-repeat:no-repeat; background-position: middle middle;}