Answer:
The three-chambered hearts of amphibians and nonbird reptiles are facultative, allowing variation in blood flow through the heart.
Explanation:
In Anatomy, cardiac cycle can be defined as a complete heartbeat of the human heart which comprises of sequential alternating contraction and relaxation of the atria and ventricles, therefore causing blood to flow unidirectionally (one direction) throughout the human body.
Generally, the cardiac cycle occurs in two (2) stages;
I. Diastole : in this stage, the ventricles is relaxed and would be filled with blood.
II. Systole: at this stage, the muscles contracts and thus, allow blood to be pushed through the atria.
All amphibians and reptiles except for crocodiles (having four-chambered heart) have three-chambered hearts, which typically comprises of a partially divided ventricle and two atria.
Hence, the correct statement about the three-chambered hearts of amphibians and nonbird reptiles is that, the three-chambered hearts of amphibians and nonbird reptiles are facultative, allowing variation in blood flow through the heart due to the partially divided ventricle.
It contracts and relaxes!
Hope this helped u!!
Answer:
B) The normal pH of blood is 6.8 to 7.0.
Explanation:
The blood pH under normal health conditions is between 7.35 and 7.45. Below this range, blood pH is considered more acidic than normal, and it may indicate that the body is eliminating a lower amount of 
than normal, or that there is a decrease in the concentration of 
or accumulation of acid in the blood due to poisoning or disease.
The process responsible for this is mass movement.
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PCR is a useful technique because it is used to amplify small segments of DNA.
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