2. If $\log _{N} N=\log _{N} M$, where $M \neq N, M$ $\neq 1, N \neq 1$, then $M N$ equals ( ).
(A) 1
(B) 2
(C) 10
(D) $\frac{1}{4}$
A

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