题目

It is 8:45 a. m. and a line of hungry children eagerly await breakfast outside a classroom. Moments later they burst in, running over to a table covered with cereals, spreads, milk and juice to enjoy a satisfying, healthy breakfast. This is familiar for Cannel McConnell, founder of The Magic Breakfast, a charity that delivers morning meals to children who would otherwise go without. Ms McConnell created her organization 16 years ago after hearing from school staff that they had to feed their pupils before lessons started, as many were so hungry as to sleep in class. The Magic Breakfast ha 某同学在做“用单摆测定重力加速度”的实验中，如果他测得的g值偏小，可能的原因是 [　　] A． 测摆线长时，摆线拉得过紧 B． 摆线上端未牢固地悬挂，振动中出现松动，使摆线长度增加了 C． 开始计时时，秒表过迟按下 D． 实验中误将49次全振动记为50次