Match each cation in List I with the effect that is mainly responsible for its stability (or instability) in List II. List I: P: $\mathrm{CH}{}_3-\mathrm{O}-\mathrm{CH}{}_2{}^{+}$; Q: $(\mathrm{CH}{}_3){}_3\mathrm{C}{}^{+}$; R: $\mathrm{C}{}_6\mathrm{H}{}_5\mathrm{CH}{}_2{}^{+}$; S: cyclopenta-2,4-dien-1-ylium (cyclopentadienyl cation). List II: 1: lone-pair donation ($+M$); 2: hyperconjugation as the only delocalisation; 3: delocalisation into a benzene ring pi system; 4: antiaromatic destabilisation.

1. AP-2, Q-1, R-3, S-4
2. BP-3, Q-2, R-1, S-4
3. CP-1, Q-2, R-3, S-4
4. DP-1, Q-2, R-4, S-3