已知 0<a<β<π20 < a < \beta < \frac{\pi }{2}0<a<β<2π ,则( )A. sina−sinβ<a−β\sin a - \sin \beta < a - \betasina−sinβ<a−β B. a−β<tana−tanβa - \beta < \tan a - \tan \betaa−β<tana−tanβC. asinβ<βcosaa\sin \beta < \beta \cos aasinβ<βcosa D. tanβ>aβ\tan \beta > {a\beta }tanβ>aβ