请解题---**Question Number:** 4. **Question Stem:** 如图,一只甲虫在 5×5 的方格(每小格边长为 1)上沿着网格线运动.它从 A 处出发去看望 B、C、D 处的其它甲虫,规定:向上向下向右走均为正,向下向左走均为负.如果从 A 到 B 记为: A→B (+1, +4),从 B 到 A 记为: B→A (-1, -4),其中第一个数表示左右方向,第二个数表示上下方向. **Image Description:** * **Type:** Grid diagram. * **Dimensions:** A 5x5 grid of squares. Each small square has a side length of 1. * **Points:** Four points are labeled on the grid lines: A, B, C, and D. * Point A is located at the bottom-left corner of the grid. * Point B is located 1 unit right and 4 units up from point A. * Point C is located 3 units right and 4 units up from point A. * Point D is located 4 units right and 2 units up from point A. * **Coordinate System/Movement Rule:** * Rightward movement is positive (+). * Leftward movement is negative (-). * Upward movement is positive (+). * Downward movement is negative (-). * Movement is recorded as (horizontal movement, vertical movement). **Sub-question (1):** 图中 A→C(______, ______); B→C(______, ______); C→______(+1, -2); **Sub-question (2):** 若这只甲虫从 A 处去甲虫 P 处的行走路线依次为 (+2, +2), (+2, -1), (-2, +3), (+2, +1), 请在图中标出 P 的位置; **Sub-question (3):** 若图中另有两个格点 M、N,且 M→A(2-a, b-4), M→N(5-a, b-3), 则 N→A 应记为什么? 直接写出答案.