C. the crust and upper mantle 
        
                    
             
        
        
        
Answer:
oxygen enters blood cells by 'diffusion'
 
        
             
        
        
        
Answer:
Increased exposure to X-rays
Explanation:
X-rays shoot harmful radiation through your body, that's why when you go to the dentist or other places and they take a X-ray they give you a lead vest to protect your organs from unneeded radiation.
hope this helps :)  
 
        
             
        
        
        
 This information can be useful to agriculture because bees are major pollinators of crops, so it is important to know which pesticides to manage in order to avoid risk to bee survival. That is option B.
Bees are one of the social insects that lives in societies that are based on a caste system.
Each caste performs a special task or series of tasks that serves as an economic importance to the agricultural system.
Pests such as parasitic mites cause poor agricultural yield. By using pesticides, which are protective chemicals, farmers have greatly improved crop yield.
The bee workers while in search of pollen from crops can be harmed from the pesticides that is being used to control parasitic mites. This can lead to Colony collapse disorder of the caste system of bees. 
Therefore,  it is important to know which pesticides to manage in order to avoid risk to bee survival.
Learn more here:
brainly.com/question/22575738
 
        
             
        
        
        
Explanation:
Genetic variation is increased by meiosis
Because of recombination and independent assortment in meiosis, each gamete contains a different set of DNA. This produces a unique combination of genes in the resulting zygote. Recombination or crossing over occurs during prophase I