单项选择题

A.1-((Yt-Y^t)2/(n-1))/((Yt-Yt)2/(n-k))
B.1-(1-R2)*(n-1)/(n-k)
C.1-(1-R2)*(n-k)/(n-1)
D.1-(1+R2)*(n-k)/(n-1)