Answer: in order for a scientific investigation to be valid A hypothesis must be tested throughout a Scientific investigation that can gather evidence and support it. 
Explanation: in any scientific investigation you have to have a testable hypothesis, without your hypothesis it’s not really a scientific investigation.
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Cytoplasm,is it cell orangans? If so cytoplasm
        
                    
             
        
        
        
Answer:
A. Biodiversity will decrease .
Explanation:
- The loss of a keystone species can cause extinction  or mass destruction of other species that are dependent on it because keystone species are those species which significantly influence the existence and survival of other species in an ecosystem
- Since, beavers are considered as the keystone species, their removal  from the ecosystem will cause loss of many other species in the ecosystem resulting in Decrease in the biodiversity of that ecosystem.