Answer:
B
Step-by-step explanation:
Using the rules of exponents
[tex]a^{m}[/tex] × [tex]a^{n}[/tex] ⇔ [tex]a^{(m+n)}[/tex] and
[tex]a^{0}[/tex] = 1, then
[tex]9^{x}[/tex] × [tex]9^{-x}[/tex]
= [tex]9^{(x-x)}[/tex]
= [tex]9^{0}[/tex] = 1 → B
