在一元回归中，回归平方和是指（　　）。

A、_{<IMG src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/f65796e5-7ac3-4d45-8674-62e4d542b3ba.gif" width="87" height="51">}

B、_{<IMG src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/04b593a5-96d0-452e-b681-12bde37c33b9.gif" width="89" height="51">}

C、_{<IMG src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/c52e1fba-389c-408a-8721-179575550f58.gif" width="87" height="51">}

D、_{<IMG src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/559869d4-bf09-49c4-b2eb-f47cb0f715f5.gif" width="140" height="51">}