Answer:
D) presence of transcription activators or repressors
Explanation:
The reason why this is not post-transcriptional regulation is that activators actually start the process of transcription by binding to specific sites. while on contrary when repressor binds it halt the process.
For example, there is a protein called CAP which in the presence of cAMP bind with promoter region and enhances the activity of RNA polymerase . While in the absence of cAMP it can not bind to promoter hence the transcription stooped. 
 
        
             
        
        
        
Answer:
 The results of scientific explanation can be drawn through scientific observation and data.
Explanation:
Scientific explanations are inferred or concluded from scientific observations that was taken by the researcher because these scientific observation provides information and data to the researcher in order to formed scientific explanation from it. We can conclude scientific explanation if we have the scientific observation or in other words, The results of scientific explanation can be drawn through scientific observation and data.
 
        
             
        
        
        
Yes the o horizon layer is where most plant life is like in a forest it where all the roots of grass is
        
                    
             
        
        
        
Answer:
Tyrosine derived neurotransmitters
Explanation:
These neurotransmitters are produced as a result of the conversion of tyrosine when not incorporated into proteins or energy production is converted to catecholamines. 
These catecholamines includes dopamine, norepinephrine, and epinephrine. 
All these three catecholamines produce various effects in numerous locations in the body acting either as a neurotransmitter or as a hormone
 
        
             
        
        
        
A. is your correct answer