帮我解答---Here is the extraction of the content from the image: **二、选择题:** 本题共 4 小题, 每小题 5 分, 共 20 分。在每小题给出的四个选项中, 有多项符 合题目要求。全部选对的得 5 分, 选对但不全的得 3 分, 有选错的得 0 分。 7. 如图, A(0,0)、B(4,0)、C(0,3) 在 xy 平面内, 两波源分别置于 A、B 两点。t = 0 时, 两波源从平衡位置起振, 起振方向相同且垂直于 xy 平面。频率均为 2.5Hz。两波源持续产生振幅相同的简谐横波, 波分别沿 AC、BC 方向传播, 波速均为 10m/s。下列说法正确的是 ([ ]) **Chart/Diagram Description:** * **Type:** Coordinate system with labeled points. * **Coordinate Axes:** X-axis labeled "x/m", Y-axis labeled "y/m". Origin is at (0,0). X-axis has markings from 0 to 5 with increments of 1. Y-axis has markings from 0 to 4 with increments of 1. * **Points:** Point A is at (0,0). Point B is at (4,0). Point C is at (0,3). * **Lines:** A straight line segment connects point B and point C. A straight line segment connects point A and point C. * **Labels:** Points A, B, and C are labeled. The axes are labeled and have units (m). **Options:** A. 两横波的波长均为 4m B. t = 0.4s 时, C 处质点加速度为 0 C. t = 0.4s 时, C 处质点速度不为 0 D. t = 0.6s 时, C 处质点速度为 0