How many energetically equivalent resonance structures exist for the oxalate dianion?

The most acidic proton and the strongest nucleophilic nitrogen in the following compound

respectively, are

Among the given species the Resonance stabilised carbocations are:

Given below are two statements :

Statement I : Hyperconjugation is a permanent effect.

Statement II : Hyperconjugation in ethyl cation $\left({\mathrm{CH}}_3-\stackrel{+}{\mathrm{C}}{\mathrm{H}}_2\right)$ involves the overlapping of ${\mathrm{C}}_{{\mathrm{sp}}^2}-{\mathrm{H}}_{1\mathrm{s}}$ bond with empty $2\mathrm{p}$ orbital of other carbon.

Choose the correct option:

The chlorine atom of the following compound

that reacts most readily with ${\mathrm{AgNO}}_3$ to give a precipitate is

The following effect is known as___

The order of stability among the following alkenes is:

i 

ii 

iii 

iv 

The correct order of decreasing of reactivity towards ${\mathrm{H}}_3{\mathrm{PO}}_4$ of the following compounds is