6. Given $x \geqslant \frac{5}{2}$, then $f(x)=\frac{x^{2}-4 x+5}{2 x-4}$ has
A. Maximum value of $\frac{5}{4}$
B. Minimum value of $\frac{5}{4}$
C. Maximum value of 1
D. Minimum value of 1
6. $\mathrm{D}$ Hint: The original expression can be transformed into $\frac{1}{2}\left[(x-2)+\frac{1}{x-2}\right] \geqslant 1$.