Oxygen and carbon dioxide travels to and from tiny air sacs in the lungs, through the walls of the capillaries, into the blood. Blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs.

Answer:
When seeking to determine the number of shirts made by employees subjected to noise with and without the use of headphones, the dependent variable is the number of shirts made by the employee.
Explanation:
In a study or research, the dependent variable is the result of the intervention on the independent variable, which can be modified. In the case presented, the dependent variable is the quantity of shirts made by the employees, the number of which is measured at the end of the study.
It is expected that those employees who block the noise using headphones produce a greater number of shirts than those exposed totally or partially to noise.
For the other options:
- <u><em>The amount of noise</em></u><em>. This can modified by the use or not of headphones and is the independent variable, subject to modification.</em>
- <u><em>The type of music the employees listen to while they work</em></u><em>. Does not represent dependent or independent variable.</em>
- <u><em>The amount of training employees need</em></u><em>. It is not the variable being studied.</em>
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The group in an experiment that all the conditions stay the same is the control group.
Answer:
meiosis
Explanation:
Down syndrome is an abnormality that occurs on chromosomes 21, it occurs because chromosomes 21 cannot be separated in meiosis, the pair of chromosomes 21 do not separate and go together to one of the daughter cells. In this way, the oocyte or the resulting sperm will have 24 chromosomes instead of 23. When in conception that oocyte or sperm joins the germ cell of its partner that contributes the 23 chromosomes, the total sum of chromosomes that will have the first cell of the new conceived being will be 47.