When an ordinary computer mouse get dirty, it has to be replaced with a new one.（）
The key components of a computer mouse are the two LED.（）
When an ordinary computer mouse get dirty, it has to be replaced with a new one.（）
The most durable computer mice on sale are the IBM ones.（）
The optical mouse is superior to the basic in that the former has no moving parts.（）
The Channel Tunnel was closed for 10 hours after the earthquake occurred.（）
