Answer:
C) A changed to G in the first position of the codon.
Explanation:
In the translation of DNA,  triplets  or codons of mRNA  (a group of three nucleotides) are read according to a genetic code, to build proteins. 
Proteins are composed of amino acids. In the translation process, each codon codes for an particular amino acid according to the  genetic code as illustrated  in the DNA codon table (attached here).  
In this table we can see that if the first position  of any of the codons coding for Threonine ( ACT, ACC, ACA, ACG) is changed for G, Adenine is going to be encoded instead of threonine.
 
        
             
        
        
        
Xylem and phloem 
hope u got it right
        
                    
             
        
        
        
Answer:
Environmental impacts of particles, such as dust and  smoke, released from livestock production - impair the visibility, can lead to acid rain, degrade the ecosystem
Environmental impacts of greenhouse gases released from livestock  production -  increase in atmospheric temperature 
Explanation:
Environmental impacts of particles, such as dust and  smoke, released from livestock production - 
Release of particles such as  dust and  smoke is referred to as particulate pollution. These particle makes the air unfit for .breathing. If humans inhale it, it will adversely affect the heart and lungs. 
These particle impair the visibility, can lead to acid rain, degrade the ecosystem etc. 
Environmental impacts of greenhouse gases released from livestock  production - 
Green house gases will lead to increase in atmospheric temperature 
 
        
             
        
        
        
<span>Electrical signals in the body are often based on ions because ions are charged particles</span>