Calcium is obtained by which of the following methods?

In transgenics,the expression of a transgene in the target tissue is determined by:

The reagent used for converting acetylene to oxalic acid is

Aluminium chloride exists as a dimer,$Al_2Cl_6$,in the solid state as well as in solutions of non-polar solvents such as benzene. When dissolved in water,it gives:

What is the composition of the white enamel of our teeth?

The angle of elevation of a stationary cloud from a point $2500 \ m$ above a lake is $15^{\circ}$ and from the same point the angle of depression of its reflection in the lake is $45^{\circ}$. The height (in metres) of the cloud above the lake,given that $\cot 15^{\circ}=2+\sqrt{3}$,is