指出下列选项中划线字读音有误的一项（      ）

某同学设计了一个探究加速度a与物体所受合力F及质量m关系的实验，如图甲所示为实验装置简图．

 正确的实验操作是科学探究成功的基础，下列操作中错误的是（　　）

任务型阅读

     My name is Chen Yang. I'm twelve years old. I'm a Chinese student.

     There are four people in my family—my father, my moth er, my brother and I. My father is a doctor at the City Central Hospital and my mother is a theatre manager. My brother is a student, too. He is thirteen. We are in the same school, but not in the same class.

I like English very much. I can speak a lot of English. I want to have an American pen friend. Let's be friends, OK? Please write to me. My address is No. 22 Middle Sc hool, Hunan, China. My email is Cheny @ hotmail. com.

阅读短文, 回答问题。

如图所示，在粗糙水平面上放置A，B，C，D四个小物块，各小物块之间由四根完全相同的轻弹簧相互连接，正好组成一个菱形，∠BAD=120°，整个系统保持静止状态．已知A物块所受的摩擦力大小为f，则D物块所受的摩擦力大小为（   ）