The period during which the presence of  stromatolites decline is the Proterzoic period. Stromatolites are widely distributed sedimentary structures consisting of laminated carbonate or silicate rocks, produced over geologic time by the trapping, binding, or the precipitating of sediment by groups of microorganisms, primarily cyanobacteria. 
        
                    
             
        
        
        
Hazards are placed at the root of the tree and determining the cause of the hazard is the correct option for the following hazard analysis questions.
Fault Tree Analysis (FTA) explores how selected “top” faults (abnormal conditions) or fault events such as accidental/unwanted releases of hazardous materials can be resolved to their causes. Hazard analysis is defined as the process of gathering and interpreting information about the hazards and conditions leading to their existence in order to determine what is food safety related and must be addressed in the HACCP plan. Hazard analysis is used as the first step in the risk assessment process. The result of hazard analysis is the identification of different types of hazards. A hazard is a potential condition that may or may not exist.
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I think the answer is {b.false}
Infectious diseases are diseases that spread from one person to other either directly or indirectly. I think this is the answer.
        
             
        
        
        
Answer:
d they respond to pathogens 
 
        
             
        
        
        
 
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