The control group in this experiment is the group of tomatoes that do not receive any fertilizers i.e. fourth tomato plants. 
<h3>What is Fertilizer?</h3>
Fertilizer may be defined as any chemical or natural substance which is added to the soil with the intention of enhancing productivity. 
All those groups of tomatoes in which fertilizers are added behave as a reference group while those in which fertilizer is not added behave as a control group. 
Therefore, it is well described above.
To learn more about Fertilizers, refer to the link:
brainly.com/question/24544067
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Answer:
Decreases
Explanation:
There is less air above us as we go up.
 
        
             
        
        
        
Answer :There was enough oxygen in the atmosphere to support a major burst of life on Earth
Explanation:
The Great Oxygen Event marks the time, approximately 2.5 billion years ago, when there was enough oxygen in the atmosphere to support a major burst of life on Earth
For the first half of the Earht's history, there was no oxygen in the atmosphere. It was inhabited only by single-celled organisms.Of  those simple life forms, the cyanobacteria may have. evolved a way to take energy from sunlight, and used it to make sugars out of water and carbon dioxide. They used the same chemical process we know as photosynthesis. This released vast quantities of oxygen into the atmosphere and  triggered the evolution of complex life.
 
        
             
        
        
        
Explanation:
Which process is a physical change?
c. melting ice
If you break a piece of glass, the shape of the glass changes, but the properties in the fragments remain the same. Which of the following has occurred?
d. a physical change
A substance made up of two or more elements that have been chemically combined is called
c. a compound
Of the three ordinary states of matter, gas is the only state that
c. is highly compressible
 In which state of matter do the particles have the most energy?
b. gas
Elements in group 18 called Noble Gases are highly reactive because they have 1 valence electron.
false
Atomic mass is the sum of
b. protons and neutrons
The current model of the atom is known as
a. Rutherford's model
Most elements on the periodic table are
d. metals
Which is not a quality of a non-metal?
a. shiny
Hope this helps.
 
        
             
        
        
        
Answer:
Organelle (oppitional, I don't put this on my paper but you can if you want), cells, tissues,  
Explanation: