What type of reaction is oxidative rancidity?

Among the given species,which carbocations are resonance stabilized?

The most stable carbocation among the following is:

Which of the following is the most stable cation?

Rank the transition states that occur during the following reaction steps in order of increasing stability (least $\to$ most stable):
$1.$ $CH_3-O^+H_2 \to CH_3^+ + H_2O$
$2.$ $(CH_3)_3C-O^+H_2 \to (CH_3)_3C^+ + H_2O$
$3.$ $(CH_3)_2CH-O^+H_2 \to (CH_3)_2CH^+ + H_2O$

Arrange the following anions in decreasing order of their stability:
$CH_3^{\Theta}, NH_2^{\Theta}, OH^{\Theta}, Cl^{\Theta}$