The maximum interval between two Sessions of Parliament is six months. This means that there should not be a gap of more than six months between the end of one session and the beginning of the next session of Parliament.

Option 1: Three months is incorrect. It is too short of a time period for the maximum interval between sessions.

Option 2: Four months is incorrect. It is also too short of a time period for the maximum interval between sessions.

Option 4: Nine months is incorrect. It is too long of a time period for the maximum interval between sessions.

Therefore, the correct answer is option 3: Six months, as stated above.