Explanation

Let's calculate the cost per kilogram:

3 kg costs 150 rupees, so the cost per kilogram is:

150 rupees ÷ 3 kg = 50 rupees per kilogram

To find the cost of 7 kg apples, multiply the cost per kilogram by 7:

50 rupees/kg × 7 kg = 350 rupees

So, the correct answer is: Rs. 350.