TASK DEFINITION: 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.
PROBLEM: Sentence1: Animals behave in a variety of ways which enhance their chances of survival and reproduction. 
Sentence2: Animals learn to behave to increase chances of survival.

SOLUTION: behave

PROBLEM: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: Allergens can trigger asthma attacks.

SOLUTION: allergen

PROBLEM: Sentence1: Fungi lack chlorophyll, so they cannot make food by photosynthesis as plants can. 
Sentence2: Fungi cannot absorb solar energy and cannot make food by photosynthesis as plants can.

SOLUTION:
Fungi