The best answer to the question above would be letter d. The sentence presented which is 'Researchers helped further the biological perspective when they demonstrated that electrical stimulation of the brain could evoke emotional responses in animals.' demonstrates how new discoveries can influence perspectives.
They evolved over time from older species.<span>
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<span>Not every member of a particular species (one kind of organism) must be able to reproduce in order for the species to survive. If you take homo sapiens for example (Humans) there are many males and females around the world who are sterile and unable to reproduce, yet you still see the human species flourishing. </span>
