(1) The varying number of muscle fibers that contract
<span>In most muscles, the number of muscle fibers in different motor units ranges from a few to hundreds. The nervous system can thus regulate the strength of contraction in a muscle by determining how many motor units are activated at a given instant and by selecting large or small motor unties to activate. </span>
some muscles are almost always partially contracted. In such muscles, the nervous system my alternate activation among the motor units, reducing the length of time any one set of fibers is contracted. Prolonged contraction can result in muscle fatigue due to the depletion of ATP and dissipation of ion gradients required for normal electrical signals.ing.
<span>(2) varying the rate at which muscle fibers are stimulated </span>
<span>single action potential produces a twitch lasting about 100 msec or less. If a second action potential arrives before the muscle fiber has completely relaxed, the two twitches add together, resulting in greater tension. Further summation occurs as the rate of stimulation increases. When the rate is so high that the muscle fiber cannot relax at all between stimuli, the twitches fuse into one smooth, sustained contraction called tetanus.</span>
Answer: The correct answer is D) Point.
Point is represented by a dot, which has no width, length or height.
On the other hand, angle is a figure formed with the help of two rays, which share a common end point.
Line is a segment, which consists of two end points whereas ray is a part of line having only one end point. Therefore, angle, line, and ray all three have width or length.
Thus, the correct option is Point.
Look here for an indepth explanation
<span><span>https://www.boundless.com</span>/.../evidence-of-evolution-498-11724</span><span>
</span><span><span>planetward.org/files/change_over_time</span>0001.pdf</span><span>
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Answer:
True
Explanation:
Diffusion is a passive process (no energy required) in which the substance such as liquid and gases moves from an area of high concentration to an area of low concentration.
During respiration, carbon dioxide diffuses from the blood into the alveoli and oxygen diffuses from alveoli to blood across the respiratory membrane. The partial pressure of oxygen is low in the blood of the pulmonary capillaries and high in the alveoli. so diffusion allow movement of oxygen across the respiratory membrane from the alveoli into the blood.
Hence, the given statement is true.
The answer is: D. all of the above.
When Earth receives energy from the Sun, some energy is reflected back into space, some is absorbed by the atmosphere, and some is absorbed by land and water on Earth's surface.
