Problem: How does the sentence end?

The razor cannot shave the top of the desk and John used a jack plane instead. The 
Answer: razor is weak.

Problem: How does the sentence end?

William held Derrick's hand as they got their blood drawn for tests, because 
Answer: Derrick was afraid.

Problem: How does the sentence end?

The letters on the sign were easier to read than those on the blackboard, because the 
Answer: sign was larger.

Problem: How does the sentence end?

I hired a tutor and my brother went to extra classes. He ended up getting better grades than me so the 
Answer:
extra classes must be pretty effective.