If $a + b + c = 0$, then the value of $a^3 + b^3 + c^3$ is equal to

Which of the following expression is a polynomial? Justify your answer.

$8$

Which of the following expression is a polynomial? Justify your answer.

$\sqrt{3}{x}^2-2x$

Which of the following expression is a polynomial? Justify your answer.

$1-\sqrt{5x}$

Is the following expression is a polynomial? Justify your answer.

$\frac{1}{5x^{-2}}+5x+7$

Which of the following expression is a polynomial? Justify your answer.

$\frac{(x-2)(x-4)}{x}$

Is the following expression a polynomial? Justify your answer.

$\frac{1}{x+1}$

Which of the following expression is a polynomial? Justify your answer.

$\frac{1}{7}{a}^3-\frac{2}{\sqrt{3}}{a}^2+4a-7$

Which of the following expressions are polynomials? Justify your answer.

$\frac{1}{2x}$