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.

Sentence1: All chemical reactions require activation energy to get started. 
Sentence2: Catalysts lower the activation energy.
activation

Sentence1: Secondary accidents are a major problem under driving conditions of reduced visibility. 
Sentence2: Bad weather increases the risk of car accidents.
Secondary

Sentence1: habitat destruction causes animals to move to find shelter in another habitat. 
Sentence2: ocean destruction causes animals to move to find shelter elsewhere.

animals