没有互联网的世界曾经被认为是难以想象的。

A world without the internet was once considered ___unthinkable.

对许多人来说，没有电脑工作现在是难以想象的。

For many people, working without a computer is now ___unthinkable.

允许这样的环境破坏继续在道德上是难以想象的。

Allowing such environmental damage to continue is morally ___unthinkable.