Answer:
1.) Why does menstruation begin?
A.) Period happens because of changes in hormones in the body. 
2.) How long does the menstrual cycle usually last?
A.) the menstrual cycle lasts 21 to 35 days while bleeding between 2 to 7 days
<u>-TheUnknownScientist</u>
 
        
             
        
        
        
C- argon 
This is because, an electrolyte is a solution that conducts electricity due to the presence of ions, and since argon is an atom and not an ion, it cannot conduct. Thus, it is a non-electrolyte
        
             
        
        
        
Answer:
There are two paths of a drop of blood leaving the human heart. First, the deoxygenated blood leaves the heart and second, oxygenated blood leaves the heart,
Explanation:
Deoxygenated blood leaves the heart through an artery called pulmonary artery which take this blood to the lungs. After that, oxygenated blood carries from lungs to the heart through pulmonary vein. The oxygenated blood in the heart leaves the heart through aorta and distribute this blood in all parts of the body.
 
        
             
        
        
        
Answer:
The Greeks believed in the geocentric model of the universe. 
According to this model, the Earth was present in the center whereas the Sun, moon, other planets etc revolved around it. According to Plato, the Earth was spherical in shape and it did not move. Greek philosophers, such as Aristotle and Plato, believed the Earth to be the center of the universe. All other heavenly bodies orbited around the Earth according to the Greek philosophers.
 
        
             
        
        
        
Answer:
Replication Forks
Explanation:
When replication starts, an origin of replication forms, consisting of two replication forks moving in opposite directions.
I hope it helps! Have a fantastic day!
Bored~