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.

[EX Q]: Sentence1: Leeches are external parasites. 
Sentence2: Leeches live on the surface of their hosts.
[EX A]: Leeches

[EX Q]: Sentence1: Light is the visible form of electromagnetic energy. 
Sentence2: Electromagnetic energy enters the eye through an opening called the pupil.
[EX A]: electromagnetic

[EX Q]: Sentence1: Light enters the eye through the pupil, and the pupil is made larger or smaller by the iris. 
Sentence2: When light goes through the pupil, the iris makes it larger or smaller.
[EX A]:
iris