The correct answer is speciation. 
Speciation is the term that describes the evolutionary process causing populations to evolve into different species. There are four different types of speciation: allopatric, peripatric, parapatric and sympatric. In this case, the process described is an allopatric speciation, the most common of these four types. Allopatric speciation happens when populations are geographically separated, an event that obstructs the gene flow. Since the gene flow stops, the populations evolve in response to the different environments that they live in. 
        
                    
             
        
        
        
B. Gases because it increase by less
        
             
        
        
        
Colonized countries are forced to rely on manufactured goods from their mother countries and prevents development of industry.
        
                    
             
        
        
        
Answer:
C. His mother carried at least one allele for that trait
Explanation:
-Men have a single allele of each gene on the X chromosome, inherited from their mother, and a single allele of each gene on the Y chromosome, from their father.
-A sex-linked trait is a trait that is controlled by a gene or an allele located on the sex chromosome.
-X-linked traits are maternally inherited from carrier mothers or from an affected father. Each son born to a carrier mother has a 50% probability of inheriting the X-chromosome carrying the mutant allele.
 
        
                    
             
        
        
        
Answer:
Observers ahead of the wave observe an apparent increase in wave frequency  
Explanation:
This is the Doppler Effect. The frequency of a wave increases when the source approaches the observer and decreases as the source recedes.
B, C, and D are wrong. Observers behind the source notice a decrease in frequency.