Final answer:
The greater contribution to the resonance hybrid is made by the structure that has more equal resonance contributors.
Step-by-step explanation:
The greater contribution to the resonance hybrid is made by the structure that has more equal resonance contributors. In the first pair, CH₃CH=CH⁺CH₂, there are four resonance contributors: one where the positive charge is on the central carbon atom, and three where the double bond shifts to the other carbon atoms.
In the second pair, CH₃⁺CH=CH₂, there are only three resonance contributors: one where the positive charge is on the central carbon atom, and two where the double bond shifts to the other carbon atoms. Therefore, the first structure in each pair makes the greater contribution to the resonance hybrid.