Problem: How does the sentence end?

James tried cutting the box with a blade but he failed, so he used a knife and it was a success. It appeared the 
Answer: knife is sharp.

Problem: How does the sentence end?

The carpenter used the nails on the walls and not on the doors, because the 
Answer: doors were wobbly with them.

Problem: How does the sentence end?

Rachel wanted mushrooms on the pizza, and Patricia wanted sausage, so 
Answer: Rachel said they were allergic to meat.

Problem: How does the sentence end?

We had to spray herbicide on the corn, but didn't have to for the wheat, as the 
Answer:
corn was vulnerable to disease.