What design pattern separates the code into cause and effect

This design pattern separates the code for the cause from the code for the effect -

1. Dependency Injection
2. Dependency Inversion principle
3. Iterator
4. Observer
   The above are the possible options for it. But I am unable to figure out which could be it.
   What I understand from the sentence is the code is split up into two parts.
   one part is the cause other is the effect. Sounds like Observer pattern. Any suggestions ?