Explanation:

- Option 1: Always less than the smallest resistance

- Incorrect. In series, resistances add up, resulting in a larger equivalent resistance, not less than the smallest.

- Option 2: Always greater than the largest resistance

- True. Adding resistors in series increases total resistance, so it’s always greater than any individual resistor.

- Option 3: The sum of the resistances

- Correct. In series, resistances are simply added together to find the total resistance.

- Option 4: The reciprocal of the sum of the reciprocals

- Incorrect for series. This formula applies to resistors in parallel, not in series.