Step 1: Analyzing the sentences.
- Rarely citizens are voters (A) implies that a few citizens are voters, corresponding to II. All citizens are voters.
- Citizens are never voters (B) means none are voters, corresponding to III. No citizens are voters.
- Almost all citizens are voters (C) implies that most are voters, corresponding to I. Some citizens are not voters.
- Citizens are always voters (D) suggests that all citizens are voters, corresponding to IV. Some citizens are voters.
Step 2: Conclusion.
The correct answer is Option 4.
Final Answer:
\[
\boxed{\text{The correct answer is 4. A - II, B - IV, C - I, D - III.}}
\]