Using a microscope
Explanation:
A microscope is a scientific device used for magnifying and studying very tiny features. 
It was invented by Anton Von Leeuwenhoek in the 17th century. 
- A unicellular organism is an organism made up of a single cell. 
- A multi-cellular organism is made up of several cells. 
- A cell is a very small microscopic structure. 
- It is usually described as the fundamental unit of life. 
- Due to its small size, the naked eyes cannot see it 
- The invention of the microscope opened up the world of cells. 
- Since they have been around for a long time, distinction of cells would have been made possible at those times using a microscope. 
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Microscope brainly.com/question/4065308
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The second one I think .............
        
             
        
        
        
This question is incomplete. The options are:
<span>a. be choosy about which females they mate with. 
b. be indiscriminant about which females they mate with. 
c. mate with as many females as possible. 
d. compete to mate with choosy females.
</span>
The answer is a: be choosy about which females they mate with. 
This is because the male would in this case be investing a lot of energy in parenting its young, and would therefore adopt a strategy of mating with one or very few females. It therefore makes sense that the male would be choosy in regards to its mate. 
        
             
        
        
        
The answer is A:it does not have a plasma membrane. if you need proof https://www.bing.com/search?q=does%20a%20virus%20have%20a%20plasma%20membrane&qs=n&form=QBRE&sp=-1&p... i did a simple search
        
                    
             
        
        
        
A segmented viral genome can facilitate rapid evolution of new viral strains.
Explanation:
Viruses are non-cellular entities which contain one or molecules of DNA or RNA as their genetic material enclosed inside a protein capsule.
Viruses are obligate intracellular parasites and cannot replicate outside a living cell.
The virus integrates its genome into the host genome and uses its mechanism to replicate its genome.
In other words we can say that viruses actually hijack hosts replication machinery.
The fragment of viral genome which disintegrates itself from the host genome after successful replication might carry fragments of host genome. Thus the viral genome gets modified and may evolve.