Answer: D) Pulmonary and aortic valves.
Explanation
There are two main heartbeats from a healthy heart.
The first beat is called the S1 or the lub, and it occurs when the atrioventricular valves (comprising the mitral and tricuspid valves) close.
The second beat is called the S2 or the dub, and it occurs when the semilunar valves (comprising the aortic and pulmonary valves) close.
Listening for heart beats is an essential part of cardiac auscultation.
        
             
        
        
        
Answer:
The statement that says "Energy enters a food chain as heat energy and leaves it as light energy" is false.
Explanation:
The energy that enters the food chains, first of all, is light energy from the sun. This energy is assimilated by plants to convert it into chemical energy, through  photosynthesis.
When energy flows from producers, plants, to consumers and decomposers, a great amount of <u>energy is lost, in the form of </u><u>heat energy</u>, due to the metabolism of living beings. Additionally, the second law of thermodynamics states that when energy passes from one form to another it leads to disorder in the system, which would also explain the loss of energy.
The true statement is "Energy enters a food chain as <u>light energy</u> and leaves it as <u>heath energy"</u>.
 
        
             
        
        
        
Answer:
Fraternal twins can be different genders because they are two completely different eggs getting fertilized; but even two same gender fraternal twins do not look completely alike. Whereas for identical twins since one egg is splitting into two, the two cells have the same exact DNA make up and chromosomes.
I also believe the technical part of it is to do with genetics, like ressesive and dominant genes, because they can be the same gender, ex. both girls and one has blue eyes, fair skin, and blonde hair, the other twin has brown eyes, black hair and tan skin. The parents could be part of the genes but there is also grandparents maybe the mom's mom has blonde hair and blue eyes, with fair skin. But the dad he has brown eyes, black hair and tan skin. The moms genes were recessive, but the grandma's genes were dominant.
I tried to explain it as best as I could I hope it helps!
 
        
             
        
        
        
Answer: 50%
Explanation: I used Punnet squares and past answers.
considering I used past answers it has to be correct. (the past answers were from less than a week ago)
 
        
             
        
        
        
<span>The theory of plate tectonics helps to explain the </span>formation of the earthquakes.