The correct answer to the question is option 4, which is "four." This means that there are four oil refineries in the State of Assam. It is important to note that this answer assumes that the given information is accurate and up to date. If there were any changes in the number of refineries in Assam since the information was provided, the answer may not be valid. Additionally, it is worth mentioning that the answer does not provide any further details about the oil refineries, such as their names, locations, or capacities.