Problem: Continue the following story.

the river drained the water to the ocean until its source was no longer with water, the 
Here's how I want to continue it: source was scant.

Problem: Continue the following story.

Nick is bad at writing letters, but William is great at them. This is due to 
Here's how I want to continue it: William preferring English class.

Problem: Continue the following story.

Jon had to attend more physical therapy for his knee than for his elbow. The 
Here's how I want to continue it:
elbow had the less serious injury.