The number of ways that $8$ beads of different colours can be strung as a necklace is

For the given figure,if the block remains in an equilibrium position,find the frictional force between the block and the wall in $N$.

When an air bubble of radius $r$ rises from the bottom to the surface of a lake, its radius becomes $\frac{5r}{4}$. If the atmospheric pressure is equal to the pressure exerted by a $10 \ m$ height of water column, and the temperature remains constant while surface tension is neglected, what is the depth of the lake (in $m$)?

Which of the following is different from the other three oxides?

Silviculture is the cultivation of which of the following?

Which of the following is not correct?