7. When $0<a<1$, which of the following is true?
A. $a^{a}>a^{a^{a}}$
B. $a^{a}>a^{a^{a}}>a$
C. $a^{a^{a}}>a>a^{a}$
D. $a^{a}>a>a^{a^{a}}$
7. B;

;

Translate the text above into English, please retain the original text's line breaks and format, and output the translation result directly.