The formula of sodium nitroprusside is:

The electronic configurations of four elements are given as:
$(I) 1s^2, (II) 1s^2 2s^2 2p^2, (III) 1s^2 2s^2 2p^5, (IV) 1s^2 2s^2 2p^6$. Which configuration has the ability to form both ionic and covalent bonds?

Which logic gate is represented by the following combination of logic gates?

The domestic sewage in large cities

Opening of flowers in the cymose inflorescence is

The abscissae of $A$ and $B$ are the roots of the equation $x^2+2ax-b^2=0$ and their ordinates are the roots of the equation $y^2+2py-q^2=0$. Find the equation of the circle with $AB$ as the diameter.