Problem: How does the sentence end?

The slim legs on Erin were the envy of Rebecca , since
Answer: Rebecca was ignorant of how to take care of her figure.

Problem: How does the sentence end?

Laura didn't give Victoria a reason for why they were being mean, even though
Answer: Laura owed them an explanation.

Problem: How does the sentence end?

Nick taught Christopher how to focus a camera, since
Answer: Christopher had never been able to get the hang of that.

Problem: How does the sentence end?

I bought the wrong size of tarp and it didn't fit the truck, because the
Answer:
truck was too long.