Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Q: Sentence1: Contact with infected blood, contaminated needles. 
Sentence2: scraping oneself on an infected needle may cause infection.

A: infected
****
Q: Sentence1: Parasites are organisms that live off a host. 
Sentence2: roundworms may be free-living or live off a host.

A: host
****
Q: Sentence1: skin is used for protecting the body from harmful substances. 
Sentence2: Acids are harmful to tissue.

A:
harmful
****