为了研究滑块的运动，选用滑块、钩码、纸带、毫米刻度尺、带滑轮的木板以及由漏斗和细线构成的单摆等组成如图甲所示装置，实验中，滑块在钩码作用下拖动纸带做匀加速直线运动，同时让单摆垂直于纸带运动方向做小摆幅摆动，漏斗可以漏出很细的有色液体，在纸带上留下的痕迹记录了漏斗在不同时刻的位置，如图乙所示．

Ⅰ．漏斗和细线构成的单摆在该实验中所起的作用与下列哪个仪器相同？____（填写仪器序号）．

A．打点计时器   B．秒表    C．天平

Ⅱ．已知单摆周期T=2s，在图乙中AB=24.10cm，BC=27.90cm、CD=31.80cm、DE=35.50cm，则单摆在经过D点时，滑块的瞬时速度为v_D=____m/s，滑块的加速度为a=____m/s²（结果保留两位有效数字）

    My name is Lucy and this is my grandfather．His name is Tim and he is my  best friend．My grandfather is 64 years old and he is retired now,so he has much time to be and play with me．I love him very much and I know he loves me too．

    He lives with me．my father,my mother and my brother Kevin．We live in a big house．My grandfather is a very tall and strong man!Can you see me on his shoulders (肩膀)in this picture?He is really strong!My grandfather always knows what l want to do or to eat or what I feel inside!When I am sad，he makes me laugh with his funny faces．Every night before I go to bed，my grandfather tells me stories，and he even sings for me!

根据材料内容选择最佳答案。