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: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Bamboos are vigorous, rugged plants.
[A]: Plants


[Q]: Sentence1: Ejaculation allows males to reproduce. 
Sentence2: propelling sperm from the epididymes allows males to reproduce.
[A]: allows


[Q]: Sentence1: Mammals have a layer of fat under the skin to help insulate the body. 
Sentence2: Dietary fats are the fats found in foods.
[A]:
fat