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: Ejaculation allows males to reproduce. 
Sentence2: propelling sperm from the epididymes allows males to reproduce.
[EX A]: allows

[EX Q]: Sentence1: dropping an object into water causes vibrations in the water. 
Sentence2: Dropping an object into lake causes vibrations.
[EX A]: dropping

[EX Q]: Sentence1: fog is formed by water vapor condensing in the air. 
Sentence2: Fog happens when the water vapor condenses into particles as air temperatures cool.
[EX A]:
condensing