19.已知a=1.11.2a=1.1^{1.2}a=1.11.2,b=1.21.1b=1.2^{1.1}b=1.21.1,c=log1.21.1c=\log _{1.2}1.1c=log1.21.1,则aaa、bbb、ccc的大小关系为((( )))