Into how many classes are the angiosperms (flowering plants) classified?

The pair of xenon compounds which have the same number of lone pairs of electrons on the central atom is

Which one of the following represents the correct order of electronegativity?

Which one of the following arrangements represents the correct order of electron gain enthalpy (with negative sign) of the given atomic species?

Two electric bulbs whose resistances are in the ratio of $1:2$ are connected in parallel to a constant voltage source. The ratio of the power dissipated in them is:

In the half-wave rectifier circuit shown,which one of the following waveforms is true for $V_{CD}$,the output across $C$ and $D$?