Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Fact: passive immunity lasts only as long as the antibodies survive in blood. 
Question: passive immunity lasts only as long as the antibodies survive where?
blood.

Fact: Some viruses can cause abnormal cell growth. 
Question: What be caused by some viruses?
Abnormal cell growth.

Fact: A force defined by Newton causes objects that have mass to be pulled down on a planet. 
Question: The thing that causes objects to be pulled down on a planet was defined by which scientist?

Newton.