The moment of inertia of a uniform circular disc is maximum about an axis perpendicular to the disc and passing through which of the following points?

The moment of inertia of a thin square plate $PQRS$ of uniform thickness,about an axis passing through the centre '$O$' and perpendicular to the plane of the plate is (where $I_1, I_2, I_3, I_4$ are respectively the moments of inertia about axes $1, 2, 3, 4$ which are in the plane of the plate as shown in the figure):

For the given uniform square lamina $ABCD$,whose centre is $O$,

The moment of inertia of a uniform cylinder of length $l$ and radius $R$ about its perpendicular bisector is $I$. What is the ratio $l/R$ such that the moment of inertia is minimum?

The moment of inertia of a solid sphere,about an axis parallel to its diameter and at a distance of $x$ from it,is $I(x)$. Which one of the graphs represents the variation of $I(x)$ with $x$ correctly?

The $X$ and $Z$ axes are mutually perpendicular in the plane of a disc,and the $Y$ axis is perpendicular to the plane of the disc. If the moments of inertia of the object about the $X$ and $Y$ axes are $30 \ kg \ m^2$ and $40 \ kg \ m^2$ respectively,then the moment of inertia about the $Z$ axis will be ....... $kg \ m^2$.