Answer: The answer is (D) 
Step-by-step explanation: We are to select the correct monomial from the given options which is a perfect cube.
The first option is
![y=16x^6=2\times (8x^6)=2\times(2x^2)^3\\\\\Rightarrow \sqrt[3]{y}=2x^2\sqrt[3]{2}.](https://tex.z-dn.net/?f=y%3D16x%5E6%3D2%5Ctimes%20%288x%5E6%29%3D2%5Ctimes%282x%5E2%29%5E3%5C%5C%5C%5C%5CRightarrow%20%5Csqrt%5B3%5D%7By%7D%3D2x%5E2%5Csqrt%5B3%5D%7B2%7D.)
So, this is not a perfect cube.
The second option is
![y=27x^8=x^2\times (27x^6)=x^2\times(3x^2)^3\\\\\Rightarrow \sqrt[3]{y}=3x^2\sqrt[3]{x^2}.](https://tex.z-dn.net/?f=y%3D27x%5E8%3Dx%5E2%5Ctimes%20%2827x%5E6%29%3Dx%5E2%5Ctimes%283x%5E2%29%5E3%5C%5C%5C%5C%5CRightarrow%20%5Csqrt%5B3%5D%7By%7D%3D3x%5E2%5Csqrt%5B3%5D%7Bx%5E2%7D.)
So, this is not a perfect cube.
The third option is
![y=32x^{12}=4\times (8x^{12})=4\times(2x^4)^3\\\\\Rightarrow \sqrt[3]{y}=2x^4\sqrt[3]{4}.](https://tex.z-dn.net/?f=y%3D32x%5E%7B12%7D%3D4%5Ctimes%20%288x%5E%7B12%7D%29%3D4%5Ctimes%282x%5E4%29%5E3%5C%5C%5C%5C%5CRightarrow%20%5Csqrt%5B3%5D%7By%7D%3D2x%5E4%5Csqrt%5B3%5D%7B4%7D.)
So, this is not a perfect cube.
The fourth option is
![y=64x^6=(4x^2)^3\\\\\Rightarrow \sqrt[3]{y}=4x^2.](https://tex.z-dn.net/?f=y%3D64x%5E6%3D%284x%5E2%29%5E3%5C%5C%5C%5C%5CRightarrow%20%5Csqrt%5B3%5D%7By%7D%3D4x%5E2.)
So, this is a perfect cube.
Thus, (D)
is the correct option.