Answer: Cells need to be able to survive
Explanation: they adapt
 
        
             
        
        
        
Answer: D. Hypothesis B is more useful because it suggests a way to test the relationship between heart rate and caffeine intake.
Hypothesis A and B both are suggesting that caffeine intake is related to higher heart rate. But hypothesis B is proving it more certainly by suggesting the affects of caffeine intake on heart rate. As, heart rate of most people will be higher 30 minutes after they drink a cup of coffee is testifying the fact, that higher heart rate is related with caffeine intake. 
Therefore, hypothesis B is more useful because it suggests a way to test the relationship between heart rate and caffeine intake.
 
        
                    
             
        
        
        
Increasing the light intensity increases the rate of photosynthesis, until some other factor - a limiting factor - becomes in short supply. At very high light intensities, photosynthesis is slowed and then inhibited, but these light intensities do not occur in nature.
        
             
        
        
        
I think the answer is chemosynthesis because deep ocean vents don't get sunlight.
        
                    
             
        
        
        
Answer:
The correct answer will be option-A
Explanation:
Colchicine is the drug that prevents the assembly of the mitotic spindles which halts or stops the cell cycle.
The colchicine acts by inhibiting the microtubule polymerization thus mitotic spindles which takes place after the condensation of the chromosomes during prophase and pre-metaphase.
This acts as checkpoint which can halt the cell cycle at the phase of chromosome condensation.
Thus, option-A is the correct answer.