Lactose is composed of ......... .

Match the items of column $I$ with column $II$. Select the correct option from the following:

Column $I$	Column $II$
$(a)$ $XX-XO$ method of sex determination	$(i)$ Turner's syndrome
$(b)$ $XX-XY$ method of sex determination	$(ii)$ Female heterogametic
$(c)$ Karyotype-$45$	$(iii)$ Grasshopper
$(d)$ $ZW-ZZ$ method of sex determination	$(iv)$ Female homogametic

The proton and neutron are collectively called as

$A$ body is sliding down a rough inclined plane. The coefficient of friction between the body and the plane is $0.5$. The ratio of the net force required for the body to slide down and the normal reaction on the body is $1:2$. Then the angle of the inclined plane is: (in $^{\circ}$)

The compound,found in nature in gas phase but ionic in solid state is

Magnetic fields at two points on the axis of a circular coil at a distance of $0.05\,m$ and $0.2\,m$ from the centre are in the ratio $8 : 1$. The radius of the coil is.....$m$