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The stability of a carbocation is most significantly influenced by the degree of substitution. Carbocations are electron-deficient species, and their stability is positively correlated with the number of alkyl groups attached to the positively charged carbon. Alkyl groups are electron-donating through the inductive effect and hyperconjugation, which helps to stabilize the positive charge on the carbocation.

For instance, a tertiary carbocation, which has three alkyl groups attached, is much more stable than a secondary or primary carbocation because the alkyl substituents can help delocalize and disperse the positive charge. This stabilization is crucial for the carbocation's reactivity and tendency to participate in subsequent chemical reactions.

While resonance stabilization can also play a role in carbocation stability, it is generally applicable to specific structures where resonance is available (like allylic or benzylic carbocations). Hence, while the presence of resonance can enhance stability, the overarching influence in a general context is the degree of substitution, making it the most reliable factor in assessing carbocation stability.

Factors such as the size of the carbocation and the electronegativity of adjacent atoms are less directly involved in stabilizing the positive charge than the electron-donating ability of alk