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. 
 
        
                    
             
        
        
        
Answer:
The correct option is 'C' that is eventually the population stop increasing or would decreases due to lack of food and living space.
Explanation:
In 1798, he wrote an essay on Principle of population where he described that how the population will grow with economy.
He claimed that the population will grow until the food supply decreases  and then the population will stop growing due to lack of food and space and those individuals that can fight against this condition and and could attain food, space and other essential necessities will survive.
 
        
             
        
        
        
A. they have shared matter.
        
             
        
        
        
Diffraction occurs when a wave moves through an opening in a barrier. This causes the wave to change direction and spread out.
Waves can behave in three different ways depending on the obstacles they encounter. They can reflect, refract or diffract. In diffraction, waves such as sound, light or water either bend around small objects that obstruct their passage or spread out as they travel through a gap in the barrier.
The degree of diffraction forms a direct relationship with wavelength. It generally increases as wavelength increases. Conversely, the amount of bending lessens as wavelength decreases. However, if the opening of the barrier is smaller than the wavelength, the effect of diffraction is not easily observed. Hope this helps.