Identify the halogen exchange reaction from the following.

The angle of elevation of an object on a hill is observed from a certain point in the horizontal plane through its base to be $30^{\circ}$. After walking $120 \ m$ towards it on level ground,the angle of elevation is found to be $60^{\circ}$. The height of the object (in metres) is:

The number of molecules in $16 \ g$ of methane is

$A$ polaroid is placed at $45^{\circ}$ to an incoming light of intensity $I_0$. Now,the intensity of light passing through the polaroid after polarization would be:

The point collinear with $(1, -2, -3)$ and $(2, 0, 0)$ among the following is

What do bio-pesticides include?