Refer to the attachment for periodic table
Answer:
Oxygen debt is a physiological phenomenon in which a person consume oxygen at fater rate that it replaced by new oxygen molecules.
As shown in the graph, oxygen debt occurs just after the end of exercise because oxygen is consumed at faster rate during exercise that leads to increased respiration and body attempts to replace the used oxygen.
To overcome the problem of oxygen debt, a person should take rest that allows the body to replenish its oxygen supply.
Answer:
D. tip his head back farther to open his airway.
Explanation:
Tilting the head farther back moves the tongue away from the back of the throat, allowing air to enter the lungs.

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Answer:
The conifer phylum also contains the <u><em>Gnetophyta (Gymnosperms)</em></u>, an order that includes the genera Gnetum, Ephedra, and Welwitschia.
Explanation:
That group includes 70 species across the three genera mentioned above, the difference between the Gnetophytas and other Gymnosperms plants is the presence of vessels, similar to the ones in the flowering plants.


Answer:
Substance
<u>Review</u>:
⇒ One of a class of substances that cannot be separated into simpler substances by chemical means.
<u>Compound</u>:
⇒ A pure substance composed of two or more elements who composition is constant.