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: bacteria cause food to spoil. 
Sentence2: Food poisoning occurs when spoiled food is eaten.

A: spoil
****
Q: Sentence1: lightning can cause a forest fire. 
Sentence2: Lightning can cause a natural cycle in forests.

A: lightning
****
Q: Sentence1: Coral Reefs Coral reefs are marine biomes that are unique to tropical seas. 
Sentence2: coral reefs are found in salt water of ocean.

A:
Coral
****