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What is the inverse function of [tex]y=\sqrt{x-4}[/tex] if [tex]x\ge4[/tex]

[tex]A. y=x^2+16,\:x\ge0\\B. y=x^2-16,\:x\ge0\\C. y=x^2+4,\:x\ge0\\D.y=x^2-4,\:x\ge0[/tex]