$A$ group of atoms can function as a ligand only when

How many $EDTA$ molecules are required to make an octahedral complex with a $Ca^{2+}$ ion?

$A$ person observes the top of a tower from a point $A$ on the ground. The angle of elevation of the tower from this point is $60^{\circ}$. He moves $60 \ m$ in the direction perpendicular to the line joining $A$ and the base of the tower. The angle of elevation of the tower from this new point is $45^{\circ}$. Then,the height of the tower (in metres) is

Which of the following is not a polyamide?

Which of the following is $NOT$ a harmful effect of drug abuse?

The angular resolution of a $10\,cm$ diameter telescope at a wavelength of $5000\,\mathring{A}$ is of the order of: