Answer:
sarcoplasmic reticulum deteriorates and ATP production is stopped
Explanation:
Rigor mortis is the third stage of death characterized by stiffening of joints and muscles in body. The stiffening occurs because muscles are not able to return to the relaxed state. There are two reasons for rigor mortis, depletion of ATP and increase in calcium concentration in cytosol. Due to these factors the actin-myosin crossbridge is not able to break and the muscles remain in contracted state. 
Sarcoplasmic reticulum deteriorates and calcium is released into the cytosol. Sarcolemma ( covering of muscle fiber ) also breaks down releasing extra calcium into the cytosol. Calcium is responsible for formation of actin-myosin cross bridge and when its concentration increases the bridge is formed continuously leading to stiffening of muscles and joints.  
 
        
             
        
        
        
Answer:
B. All of its cells must work together
 
        
             
        
        
        
Answer:
The purpose of the carbon cycle is to utilize the carbon by the organisms such as plant which uses carbon in the form of carbondioxide for making food. This carbon is stored in the form of glucose. When this food is eaten by the animals, it is broken down into simpler substances and carbondioxode is released in the atmosphere again. 
Some carbon is present in soil which is used by microorganisms such as bacteria. So carbon cycle is very important for the survival of life on earth. 
 
        
             
        
        
        
<span>Cytosol is the mixture of water and other molecules found inside the cell.</span>
        
                    
             
        
        
        
I believe the correct answer is: HIV is spread during unprotected sex or through contact with infected blood; it cannot be cured, but early treatment can minimize the long-term consequences.
<h2>Explanation:</h2>
Human Immunodeficiency Virus is a type of virus which causes an impairment of the immune system of the person making them susceptible to diseases such as tuberculosis, influenza and any other disease that can exploit this opportunity. It is spread by a person coming into direct contact with infected bodily fluids such as saliva during deep kissing, semen during intercourse, blood after an accident or even fluids when sharing needles and syringes for drug addicts. There is no cure but the current form of treatment slows down the virus to prevent some consequences.
<h2>Further Explanation:</h2>
The virus is enters the body through open wounds or surfaces such as the vagina or mouth where the skin is very thin and can tear. After penetrating the skin, it attaches to specific immune cells called CD8+ T-cells on points called receptors. It then enters the cell and replicates itself in the nucleus of the cell and as it goes out, it kills these immune cells making the person to have a weak immune system. The current drugs used called AntiRetroVirals (ARVs) such as the drug Zidovudin stops the virus from replicating thus reducing the total amount of virus in the body called the Viral Load. Some drugs target enzymes called proteases and reverse transcriptase that help the virus to replicate. This viral load is what is counted to estimate the total volume of HIV someone has in their body. Infected persons should use protection while having sex and also avoid sharing sharp objects to prevent transmission. They also need to take their medication to make them much more healthier in addition to taking proper balanced diets. 
Level: High School
Subject: Biology
Topic: The Immune System