What is the cytoskeleton composed of?

If $\left(\frac{2}{3}, 0\right)$ is the centroid of the triangle formed by the lines $4x^2-y^2=0$ and $lx+my+n=0$,then $l+m+n=$

Two identical balls $A$ and $B$ are released from the positions shown in figure. They collide elastically on the horizontal portion $MN$. The ratio of the maximum height attained by $A$ and $B$ after the collision will be: (neglect friction)

$\operatorname{cosec} 15^{\circ} + \sec 15^{\circ}$ is equal to :

The angle between the lines whose direction cosines satisfy the equations $l+m+n=0$ and $l^2+m^2-n^2=0$ is

From the ground state electronic configuration of the elements given below,pick the one with the highest value of second ionisation energy.