The correct answer is (c) 9 months.
Under Muslim Law, a bequest can validly be made to a child in womb, so long it is born from the date of will within the period of 9 months. This is because the Islamic view is that a child is considered to be born from the moment of conception, and therefore a bequest made to a child in womb is considered to be a bequest made to a living person.
The other options are incorrect because they are not the full 9 months that a child is in the womb. A child is typically in the womb for 9 months, although there can be some variation.