Hyperconjugation is most useful for stabilizing which of the following carbocations?

Consider the following carbocations :

(i) ${\mathrm{Cl}}_3{\mathrm{C}}^{+}$ (ii) ${\mathrm{Cl}}_2\stackrel{+}{\mathrm{C}}\mathrm{H}$ (iii) ${\mathrm{ClCH}}_2^{+}$ (iv) $\stackrel{+}{\mathrm{C}}{\mathrm{H}}_3$

The stability sequence follows the order:

The correct stability order for the following species is:

In the following carbocation $\mathrm{H}/{\mathrm{CH}}_3$ that is most likely to migrate to the positively charged carbon is

Arrange the following carbocations in order of increasing stability:

I. $({\mathrm{CH}}_3{)}_3{\mathrm{CCH}}_2^{+}$   II. $({\mathrm{CH}}_3{)}_3\stackrel{+}{\mathrm{C}}$    III. ${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2^{+}$   IV. ${\mathrm{CH}}_3-\stackrel{+}{\mathrm{CH}}-{\mathrm{CH}}_3$.

The order of stability of the following carbocations is.

I. ${\mathrm{CH}}_2=\mathrm{CH}-\stackrel{+}{\mathrm{C}}{\mathrm{H}}_2$          II. ${\mathrm{CH}}_3-{\mathrm{CH}}_2-\stackrel{+}{{\mathrm{CH}}_2}$         III.