Answer:
Our body cells require oxygen to release energy.
Explanation:
The oxygen that we take in during respiration is used to break down the food we eat to release energy from it. When we breathe in oxygen, it diffuses into blood from the lung, where it is transported by red blood cells to the entire body to be used to produce energy.
Answer:
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Explanation:
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Calcium. Calcium can be obtained from milk.
Answer:
Because the trophozoites are unable to survive outside a host.
Explanation:
The term infectious is used for a disease or microorganism that can be transmitted from one organism to the other organism through the environment. If we look at the two forms of Giardia, we find that out of the two forms viz. cysts and trophozoites, only the cysts of Giardia have the ability to remain alive in the environment outside the host and thus they are able to be transmitted to the other organisms. On the other hand trophozoites are not able to survive in outside environment so there is no chance of transmission of trophozoites.