Story needs to be completed:
Laura was jealous that Jessica was in a relationship, so

My choice:
Laura always gave them dirty looks.

Story needs to be completed:
Nick taught Christopher how to focus a camera, since

My choice:
Christopher had never been able to get the hang of that.

Story needs to be completed:
So

My choice:
Robert enjoys reading books because Robert spends a lot of time with books and Aaron outside.

Story needs to be completed:
The weather conditions were better for Donald than Hunter because

My choice:
Donald was inland from the storm.