The expression [tex]( x^{1/2}y^{-2/3})^-6 [/tex] is equivalent to

A. [tex] \frac{y^4}{x^3} [/tex]
B. [tex] \frac{x^3}{y^4} [/tex]
C. [tex] \frac{1}{x^3y^4} [/tex]
D. [tex]x^3y^4[/tex]

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