neurotransmitters is the answer
This period was the industrial revolution, in this period power-driven machines began to do work people had originally done. For example, in 1784, the first mechanical loom was created.
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Answer:
Heart valves or the closure of the mitral and tricuspid atrioventricular (AV) valves at the beginning of ventricular systole and the closure of the aortic valve and pulmonary valve at the end of ventricular systole.
Explanation:
The heart tone “lub,” or S1, is caused by the closure of the mitral and tricuspid atrioventricular (AV) valves at the beginning of ventricular systole.
The heart tone “dub,” or S2 ( a combination of A2 and P2), is caused by the closure of the aortic valve and pulmonary valve at the end of ventricular systole.
The best and most correct answer among the choices provided by the question is <span>evolution.
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Evolution is about 65% cause of the natural selection.<span>
Hope my answer would be a great help for you.</span>
