The correct answer is option 1: 6 months. When the office of the President becomes vacant, it must be filled within 6 months. This means that a new President must be elected or appointed within this timeframe.
Option 2: 12 months is not the correct answer. The vacancy of the office of the President must be filled within a shorter timeframe than this.
Option 3: 1 month is also not the correct answer. The correct timeframe for filling the vacancy is longer than this.
Option 4: 3 months is not the correct answer. The correct timeframe for filling the vacancy is longer than this.
Therefore, the correct answer is 6 months, as stated above.