The orbital picture of a singlet carbene $(:CH_2)$ can be drawn as:

The correct order of increasing stabilities of the following carbocations is:
$(i)$ Allyl carbocation
$(ii)$ Ethyl carbocation
$(iii)$ Benzyl carbocation
$(iv)$ Isobutyl carbocation

What is the order of stability of $1^{\circ}, 2^{\circ}, 3^{\circ},$ and $\overset{\oplus}{C}H_3$ carbocations?

The order of stability of the following carbocations is:
$I$. $CH_2 = CH - CH_2^+$
$II$. $CH_3 - CH_2 - CH_2^+$
$III$. $C_6H_5CH_2^+$

Match the ions given in Column-$I$ with their nature given in Column-$II$.

Column-$I$	Column-$II$
$A$. $CH_3-O^{+}=CH-CH_3$	$1$. Stable due to resonance
$B$. $F_3C^{+}$	$2$. Destabilised due to inductive effect
$C$. $(CH_3)_3C^{-}$	$3$. Stabilised by hyperconjugation
$D$. $CH_3-CH^{+}-CH_3$	$4$. $A$ secondary carbocation

The increasing order of stability of the following free radicals is: