Answer:
Sexual reproduction
Explanation:
In asexual reproduction, the same genes are transferred to the next generation because there is no combination of genes takes place so the rate of variation is very less in asexual reproduction and in sexual reproduction combination of different genes from two different parents occurs which give rise to genetic variation.
So when the plant is put in an environment where harmful bacteria are present then it will prefer sexual reproduction to bring variation in its genome so that it can get the ability to fight against these pathogenic bacteria.  
The plants that reproduced asexually will be eradicated by pathogens because they can not get the new genes to fight against the pathogen due to lack of appropriate variation in their gene.
 
        
             
        
        
        
Igneous rock are classifies as either volcanic rock or plutonic rock.
        
             
        
        
        
Answer: 
Rotifera- Microscopic animals with distinct head, neck, trunk, and foot
Bryozoa- Have a lophophore for feeding
Arthropoda- Have jointed appendages
Playthelminthes- Vibrantly colored flat-structured worms
Explanation:
 
        
             
        
        
        
Answer:
Syrup
Explanation:
The arrangement according to density; Syrup, water,cooking oil and alcohol.
The higher the density the heavier the substance, therefore the substance with the highest density, sinks first and the substance with the lowest density is left to float.