Autoinducer molecules are signalling molecules that need bacteria. In order for the autoinducer molecules to signal, the bacteria must find a way to initiate the signal and a way to respond to the signal it had created. Autoinducer molecules increase in production as the density of the bacteria cell increases.
 
        
             
        
        
        
Answer:
The answer is letter D
Explanation:
Purple, spherical-shaped organisms arranged in chainlike formations.
 
        
             
        
        
        
Prokaryotes do not have a nucleus, rather the DNA floats freely in the cytoplasm. Also, prokaryotes are much smaller than eukaryotes, and are typically bacteria or eubacteria.
Eukaryotic cells have membrane-bound organelles and nucleus, and are larger than prokaryotes. Some examples of eukaryotes are plant and animal cells. Hope this helps! :)
        
             
        
        
        
The blood vessels farthest from the heart must have valves.
The valves which are present in the blood vessels prevent the backflow of the blood back into the specific organ.
There are different valves present in the heart are:
- The tricuspid valve is situated between the right atrium and right ventricle.
- The pulmonary valve is between the right ventricle and the pulmonary artery.
- The mitral valve is between the left atrium and left ventricle.
- The aortic valve is between the left ventricle and the aorta.
Other vales which are present in the blood vessels are in leg. Leg veins do require the valves. If not present the blood will go back down into the feet because of the gravity. Thus there are various valves present in the leg veins. 
Valves in veins are bicuspid, meaning they have two flap-like structures that regulate blood flow in the vein.
To know more about the Valves, refer to this link:
brainly.com/question/12926213
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