Your answer is D
Gravel sized particals
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Answer:
Biodiversity: Tropical rainforests are areas of extremely high biodiversity compared to other ecosystems. Biologists estimate that tropical rainforests contain about 50% of the world's terrestrial plant and animal species, yet they encompass only about 6% of the world's land area.
Explanation:
 
        
             
        
        
        
Exposure to environmental tobacco smoke causes approximately 45 to 46,000 non smokers to die of heat diseases annually. Smoking harms the cardiovascular system in many ways which include; damaging the lining of arteries, reduces HDL, good choresterol, Raises LML, bad cholesterol, increases blood pressure and heart rate, it also causes the platelets to stick together in the blood stream and speeds the development of fatty deposits in the arteries among other risk factors. 
        
             
        
        
        
1. How many muscles are in the human body? 
2.What diseases affect the muscular system?
3. What are the functions of the muscular system?
4.what are two types of muscle fibre?