Problem: How does the sentence end?

Kenneth maintained concentration while Ian was constantly distracted, and therefore 
Answer: Ian wrote an uneven paper.

Problem: How does the sentence end?

Nelson got worried less often than Dennis did because 
Answer: Dennis had issues with anxiety and depression.

Problem: How does the sentence end?

My old knives would not cut through the bones because the 
Answer: bones were very strong.

Problem: How does the sentence end?

When Elena wanted to buy a new car, Emily offered go along because 
Answer:
Emily had purchased many new cars before.