题目

We often get in touch with others by phone calls,WeChat,messages or other ways nowadays.It means that we seldom write letters now.But a TV show,Letters Alive(《见字如面》),is bringing back this old habit.Letters Alive invites famous actors and actresses,but there are no funny jokes or different competitions.Instead,it’s just one person walking up to a microphone and reading a letter.The letters were written by people from different times in history.For example,in one episode(集),they read a letter written by the famous writer Xiao Hong to her younger brother in 1941.The letter shows t下列措施中，不可能改变导体电阻大小的是（　　） A．改变导体的长度 B．改变导体的材料 C．改变导体的横截面积 D．改变导体在电路中连接的位置