Answer: Sensory mechanisms are responsible for detecting the external stimuli present in the environment.
Explanation:
The sensory mechanisms help people to observe things around them through eyes, they can hear the sounds through their ears, they can feel the insect creeping on their skin by touch sensory mechanism, they can taste food which they cook through taste or gustatory receptors present on tongue and other parts of mouth cavity. 
 
        
                    
             
        
        
        
Answer:
B. In plants, there are no sister chromatids. 
 
        
             
        
        
        
Answer:
False
Explanation:
Approximately 200 out of 200 million sperms ejaculated during intercourse reach the general vicinity of the egg.  They sperms must undergo capacitation during which dilute inhibitory factors fluids of the female reproductive tract weaken the membrane of the sperm head so that head of the sperm can be broken easily when it came in contact with the egg. 
The first sperm to reach an egg isn’t the one to fertilize it because the egg is surrounded by a gelatinous membrane called the zona pellucida. Outside this layer, a layer of small granulosa cells also present. 
Therefore, it requires numerous sperm to clear a path through these barriers before one of them can penetrate the egg and fertilize it. 
 
        
             
        
        
        
<u>Answer</u>:
The two molecules generated by the Krebs cycle that pass their high-energy electrons to the electron transport are NADH and  FADH2
<u>Explanation:</u>
The kreb's cycle gives NADH and also the another hydrogen carrier which is termed as FADH2. During the process of the electron transport chain, one NADH gives rise to electrons and also the hydrogen ions, which has enough potential energy that can convert and produce 3 ATP molecules. Again in the electron transport chain the NADH and the FADH2 undergoes oxidation and releases energy in the form of the ATP. The process of generation of the ATP in the electron transport chain(ETC)  is also referred as the chemiosmotic phosphorolation.
 
        
             
        
        
        
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