Answer:
b. the number of motor units recruited
Explanation:
Recruitment of motor units is defined as the activation of several additional motor units which results into high contractile force in a muscle. A motor unit consists of the stimulating muscle fibres and one motor neuron.
Activation of motor neuron, stimulates and contracts all the muscle fibres inherited by the motor neuron. When only one motor neuron is activated, it results into a weak but distributed contraction of the muscle. Activating more motor neurons will result in activation of more muscle fibres, and thus a stronger muscle contraction.
Hence, the correct option is b.
It is a microscope small enough to see atoms.
The second sentence is correct if you mean lipids and proteins as 'materials'
That is biology and kind of science. PS, that was not a question
Trying to determine whether a fossil is a human ancestor, we should always look for skeleton or bone that make us human today.
<h3>What is bone?</h3>
Bone is a connective tissue which is metabolically active and the main function of bone is to provide mechanical or structural support as well as perform movement, and protect important organs of the body.
The bone is made up of bone cells known as osteocytes and extracellular matrix. The total number of bone human body contain is 206 bones including bones of spine, legs, arms, ribs, and skull.
Bones are made up of calcium and carbonate and they have bone marrow in which blood cells are produced. By nature bones came in category of living and they are active tissue .
There are several types of bones such as flat bones, short bones, sesamoid bones, and long bones. The function of bone is to protect vital organs of the body.
Therefore, trying to determine whether a fossil is a human ancestor, we should always look for skeleton or bone that make us human today.
Learn more about bone here:
brainly.com/question/5482443
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