The correct answer is C. 4.5 times.
Stock turnover is a measure of how many times a company sells its inventory in a year. It is calculated by dividing the cost of goods sold by the average inventory. In this case, the cost of goods sold is Rs. 3,60,000, the average inventory is (Rs. 80,000 + Rs. 1,00,000)/2 = Rs. 90,000, so the stock turnover is 3,60,000/90,000 = 4.5 times.
Option A is incorrect because it is the number of times the inventory is sold in a year. Option B is incorrect because it is the number of times the inventory is sold in two years. Option D is incorrect because it is not a possible answer.