instruction:
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.
question:
Sentence1: moss causes chemical weathering. 
Sentence2: If the moss was completely dried then it is dead.
answer:
moss


question:
Sentence1: Ice is frozen water. 
Sentence2: ice expands.
answer:
Ice


question:
Sentence1: Underground caves and caverns pose an exciting adventure to many. 
Sentence2: underground caves can be formed by carbonic acid in groundwater seeping through rock and dissolving limestone.
answer:

Underground