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* (8x^6)=2*(2x^2)^3\\\\\Rightarrow \sqrt[3]{y}=2x^2\sqrt[3]{2}.](https://img.qammunity.org/2018/formulas/mathematics/high-school/h6evy6iiy4sn3h9vu1yrglbghczcivvocq.png)
So, this is not a perfect cube.
The second option is
![y=27x^8=x^2* (27x^6)=x^2*(3x^2)^3\\\\\Rightarrow \sqrt[3]{y}=3x^2\sqrt[3]{x^2}.](https://img.qammunity.org/2018/formulas/mathematics/high-school/3lkr3y2fv704x934bdycbquw733l17fybk.png)
So, this is not a perfect cube.
The third option is
![y=32x^(12)=4* (8x^(12))=4*(2x^4)^3\\\\\Rightarrow \sqrt[3]{y}=2x^4\sqrt[3]{4}.](https://img.qammunity.org/2018/formulas/mathematics/high-school/rdr7yxy0b8e6dc5wz779wkc1h7wr1uwuyu.png)
So, this is not a perfect cube.
The fourth option is
![y=64x^6=(4x^2)^3\\\\\Rightarrow \sqrt[3]{y}=4x^2.](https://img.qammunity.org/2018/formulas/mathematics/high-school/dyzvpbljszyjwir470p5iio8v4rgf9or9m.png)
So, this is a perfect cube.
Thus, (D)
is the correct option.