이 부분이 이해가 잘 안갑니다

        public int Pop()
        {
            // Create a variable storing the return value
            int ret = _heap[0];

            // Rearrange the Heap since the root node is removed
            // move the very last data into the root node
            int lastIndex = _heap.Count - 1;
            _heap[0] = _heap[lastIndex];
            _heap.RemoveAt(lastIndex);
            lastIndex--;

            // Value comparision downwards begins
            // the index of the current node
            int now = 0;
            while(true)
            {
                // the indices of the child nodes
                int left = 2 * now + 1;
                int right = 2 * now + 2;

                int next = now;

                // move to the left if the left value is bigger
                if (left < lastIndex && _heap[next] < _heap[left])
                    next = left;
                // move to the right if the right value is bigger, which contains the previous case as well (that's why it's not else if)
                if (right < lastIndex && _heap[next] < _heap[right])
                    next = right;
                // Exit the loop if the left/right values are smaller than the current value
                if (next == now)
                    break;

                // Exchange the values
                int temp = _heap[now];
                _heap[now] = _heap[next];
                _heap[next] = temp;

                // Move to the next index
                now = next;
            }

            return ret;
        }

우선순위큐의 Pop 함수에서, 

저기 if 구문 3개가 나오는 부분에서 어째서 else if를 쓰지 않는 것인지 이해가 쉽사리 되지가 않습니다