6. If $|x-3|+|x+2|>a$ always holds, then the range of values for $a$ is ( ).
A. $a \geqslant 5$
B. $a>5$
C. $a \leqslant 5$
D. $a<5$
6. D. Let $f(x)=|x-3|+|x+2|$, then by the problem $a<f_{\text {min }}=5$.