Answer:
3. Least number of decimal places in the question
Explanation:
When adding or subtracting values, you must round your answer to the same "place" as the measurement with its last significant figure furthest to the left.
That is, you round off to the same number of decimal places as the measurement with the fewest decimal places.
1 is wrong. It is the rule for multiplication and division
2 is wrong. It includes both the rule for multiplication and division and the rule for addition and subtraction.
4 is wrong. The rule requires the fewest decimal places