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: Animals can communicate with sounds, chemicals, or visual cues. 
Sentence2: cats can communicate with sounds, chemicals or visual cues.

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

A: activation
****
Q: Sentence1: Flowers are a plant's reproductive organs. 
Sentence2: a plant's reproductive organs form on the dominant sporophyte.

A:
organs
****