12
$latex \sqrt{2^{4}}+\sqrt[3]{64}+\sqrt[4]{2^{8}}&s=1$
$latex = 2^{4\times \frac{1}{2}}+4^{3\times \frac{1}{3}}+2^{8\times \frac{1}{4}}&s=1$
$latex = 2^{2}+4+2^{2}$
$latex = 4+4+4 = 12$
Hence option [A] is correct answer.