他给沙发腿加了延长器，让座位更高更舒适。

He added leg ___extenders to the sofa to make the seat higher and more comfortable.

这些插件可以扩展视频编辑软件的功能。

These ___extenders can enhance the functionality of video editing software.

这些额外的习题册能有效延伸课堂教学时间。

These extra workbooks serve as excellent ___extenders for classroom time.