Answer:
The experiment should have more different subject groups, with each group consuming a different amount of beta carotene.
Explanation:
When designing an experiment, to determine the effect of the amount of a substance, the experimental design should be done to accommodate more than two experimental group with each group treated with different amount of the substance and also a control group. This will enable the researcher to determine the effect of the different ranges of amount.
In the example, in other to determine if vitamin A is dependent of the amount of beta carotene consumed, there should be more different subject groups, with each group consuming a different amount of beta carotene. 
 
        
                    
             
        
        
        
For the answer to the question above, I believe the answer to the question is Antidiuretic Hormone (ADH). <span>It is a  relatively small peptide molecule that is released by the pituitary gland at the base of the brain after being made nearby the hypothalamus. ADH has an antidiuretic action that prevents the production of dilute urine and it is also antidiuretic.</span>
        
             
        
        
        
I’m fine.How are
you?I hope your holiday was nice!
        
                    
             
        
        
        
The virus that infect bacteria are called bacteriophage ! Hope this helps! :)