Answer:
B. a decrease in the number of pathogens in the body
Explanation:
White blood cell includes immune cell like monocytes, macrophages, neutrophils, basophils, eosinophils, etc. These cells are responsible for fighting with the pathogens or foreign molecules and eliminate them from the body.
So when any pathogens get enter in the body these cell kills those pathogen and protect us from them. Therefore the decrease in the number of pathogens in the body is a direct indication that the white blood cells in the body are working. So the right answer is B.
 
        
             
        
        
        
Thomas Hunt Morgan, who studied fruit flies, provided the first strong confirmation of the chromosome theory. Morgan discovered a mutation that affected fly eye color. ... Based on the inheritance pattern, Morgan concluded that the eye color gene must be located on the X chromosome.
        
             
        
        
        
Answer
Operons are cluster of coordinated genes, including structural genes, an operator gene, and a regulatory gene. 
Explanation:
In the The repressible operons, The transcription is usually on and repressor is in inactive form, So the specific genes are transcribed. While a regulatory molecule act as corepressor and binds to repressor protein to activate it. The repressor protein cause the inactivation of repressible operon (as the name indicate). E.g., Tryptophan Repress the trp operon.
 A high level of product act as regulatory molecule (Corepressor) and turn off the operon, So anabolic pathways or synthesis of essential components are controlled by repressible operon.
In the Inducible operons, the transcription is usually off and repressor is in active form. So there is no transcription of genes. Specific Metabolite cause the activation of operon  e.g lactose cause the induction of lac operon.
As a metabolite induces the operon, So they control the Metabolic pathways or breakdown of a neutrient.
 
        
             
        
        
        
Answer:
they will only become water if there are no other molecules to react with it.
(does that help)
Explanation: