Which of the following is an amorphous solid?

Which of the following is the composition of a virus?

Which of the following cannot be used in Friedel-Crafts reactions?

If $C$ is the midpoint of $AB$ and $P$ is any point outside $AB$,then:

As shown in the figure,a block of mass $10 \, kg$ lying on a horizontal surface is pulled by a force $F$ acting at an angle of $30^{\circ}$ with the horizontal. For $\mu_{s} = 0.25$,the block will just start to move for the value of $F$ in $N$ is: [Given $g = 10 \, ms^{-2}$]

White vitriol is