If a law is applied retrospectively to punish an old act, what is affected?

Correct answer: Predictable law and fair process

The direct answer is D: predictable law and fair process are affected. People should be able to know beforehand which actions are illegal and what punishment may follow. Step by step: an act happens; at that time the person should be guided by the law that already exists; a later law should not normally turn an earlier lawful act into a crime and punish it; otherwise people cannot plan their conduct and authorities gain unfair power. Option A is wrong because election campaigning is not the central issue. Option B is wrong because a polling booth concerns voting arrangements. Option C is wrong because party registration is unrelated. Option D is correct because non-retrospective, clear law supports certainty and fair procedure. Memory cue: no punishment by a later-made rule for an earlier act.