B. Natural selection
Natural selection is the most important force of evolution. Other forces of evolution are mutation, gene flow and genetic drift.
Generalized anxiety tends to initially arise during the mid-teens through the mid-20s.
<span>Anxiety disorders are the most common mental illness in the U.S., affecting 40 million adults in the United States age 18 and older. </span>Generalized anxiety disorder tends to occur with other anxiety disorders and with depression. Because the comorbidity is so high, researchers believe that many of the factors involved in predicting anxiety disorders, in general, are particularly important for understanding Generalized anxiety disorder.
c). The human heart is about the size of an adult's fist.
A fist-sized organ, the heart circulates blood throughout your body. It serves as your circulatory system's main organ.
Four major muscle-driven chambers make up your heart; they are each powered by electrical impulses. Your nervous system and brain control how your heart beats.
The main organ of your circulatory system, a web of blood vessels that circulates blood throughout your body, is your heart. It also interacts with other bodily systems to regulate your blood pressure and heart rate. Your lifestyle, family history, and medical history are all factors that determine how well your heart functions.
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it would be Dissecting Microscope :)