Which of the following pairs of animals represents jawless fishes?

If one were to apply the Bohr model to a particle of mass $m$ and charge $q$ moving in a plane under the influence of a magnetic field $B$,the energy of the charged particle in the $n^{th}$ level will be:

If the roots of the equation $x^2+px+q=0$ are $\alpha$ and $\beta$,and the roots of the equation $x^2-rx+s=0$ are $\alpha^4$ and $\beta^4$,then the roots of the equation $x^2-4qx+2q^2-r=0$ will be

If $x^2+y^2=t+\frac{1}{t}$ and $x^4+y^4=t^2+\frac{1}{t^2}$,then $x^3 y \frac{d y}{d x}$ is equal to

$\sqrt[3]{61 - 46\sqrt{5}} = $

Seven white balls and three black balls are randomly arranged in a row. The probability that no two black balls are placed adjacently is