Select the correct answer. The energy entering this system is equal to the energy leaving the system. Based on the law of conservation of energy, how many units of energy are entering the system? Illustration of squared labeled system. The arrows on the right side line of the square and the bottom line of the square are pointing out with energy values 10 and 5 units. The arrow on the top line with question mark is facing into the square. A. 5 units B. 10 units C. 15 units D. 20 units