设 a=14, b=2ln(sin18+cos18), c=54ln54a = \frac{1}{4},\;b = 2\ln \left( {\sin \frac{1}{8} + \cos \frac{1}{8}}\right) ,\;c = \frac{5}{4}\ln \frac{5}{4}a=41,b=2ln(sin81+cos81),c=45ln45 ,则( )A. a<b<ca < b < ca<b<c B. b<a<cb < a < cb<a<c C. a<c<ba < c < ba<c<b D. c<b<ac < b < ac<b<a