请解析这道题目---**1. Question Stem:** 4. 一个小石块从空中的某一高度由静止开始竖直下落。若不计空气阻力，从小石块开始下落至刚落到地面的过程中，小石块的重力势能 Eₚ 随着时间的变化图像可能是（ ）。 **2. Options:** * **Option A:** * **Chart Type:** 2D Cartesian coordinate system. * **Main Elements:** * **Coordinate Axes:** Horizontal axis is labeled `t` (representing time), vertical axis is labeled `E_p` (representing gravitational potential energy). The origin is labeled `O`. * **Line:** A straight line starting from a positive value on the `E_p` axis (at `t=0`) and decreasing linearly to `E_p=0` at a positive `t` value on the `t` axis. * **Option B:** * **Chart Type:** 2D Cartesian coordinate system. * **Main Elements:** * **Coordinate Axes:** Horizontal axis is labeled `t` (representing time), vertical axis is labeled `E_p` (representing gravitational potential energy). The origin is labeled `O`. * **Curve:** A curved line starting from the origin `O` (`E_p=0` at `t=0`) and increasing non-linearly (concave up) as `t` increases. * **Option C:** * **Chart Type:** 2D Cartesian coordinate system. * **Main Elements:** * **Coordinate Axes:** Horizontal axis is labeled `t` (representing time), vertical axis is labeled `E_p` (representing gravitational potential energy). The origin is labeled `O`. * **Curve:** A curved line starting from a positive value on the `E_p` axis (at `t=0`) and decreasing non-linearly to `E_p=0` at a positive `t` value on the `t` axis. The curve is concave down (its slope becomes steeper as `t` increases, or it curves towards the t-axis). * **Option D:** * **Chart Type:** 2D Cartesian coordinate system. * **Main Elements:** * **Coordinate Axes:** Horizontal axis is labeled `t` (representing time), vertical axis is labeled `E_p` (representing gravitational potential energy). The origin is labeled `O`. * **Curve:** A curved line starting from a positive value on the `E_p` axis (at `t=0`) and decreasing non-linearly to `E_p=0` at a positive `t` value on the `t` axis. The curve is concave up (its slope becomes less steep as `t` increases, or it curves away from the t-axis).