20. 已知实数aaa满足loga13<1,(13)a<1,a12<1lo{g_a}\frac{1}{3}<1,{({\frac{1}{3}})^a}<1,{a^{\frac{1}{2}}}<1loga31<1,(31)a<1,a21<1,则实数aaa的取值范围是((( )))