In the given structure what does the ‘?’ indicate?

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Class 12 Biology Practice Test: Organisms and Populations - Population Growth — practice the complete quiz, review flashcards, or try a random question.


In the given structure what does the ‘?’ indicate?<br /><img src='https://www.fatskills.com/class12science/biology-aptitude-test-class-12-q15.png' alt='The population density the number of individuals in a unit area' width='400' height='400' />