What is the $SI$ unit of the radius of gyration?

Point masses $1, 2, 3$ and $4 \text{ kg}$ are located at the points $(0,0,0), (2,0,0), (0,3,0)$ and $(-2,-2,0)$ respectively. The moment of inertia of this system about the $x$-axis will be: (in $\text{ kg m}^2$)

Moment of inertia of a solid sphere about its diameter is $I$. It is then casted into $27$ small spheres of same diameter. The moment of inertia of each new sphere is

Four identical uniform solid spheres,each of same mass '$M$' and radius '$R$',are placed touching each other as shown in the figure with centers $A, B, C, D$. If $I_{A}, I_{B}, I_{C}, I_{D}$ are the moments of inertia of these spheres respectively about an axis passing through their centers and perpendicular to the plane,then:

We have two spheres,one solid and one hollow. Their moments of inertia about their respective diameters are equal. The ratio of their radii will be:

$A$ thin uniform rod of length $L$ and mass $M$ is bent at the middle point $O$ at an angle of $45^{\circ}$ as shown in the figure. The moment of inertia of the system about an axis passing through $O$ and perpendicular to the plane of the bent rod is: