The defecation reflex involves two postive feedback loops. these loops are the stretch receptors in the rectal walls and the sacral parasympathetic system. Defecation reflex empties the rectum by peristaltic movements push fecal matter from the sigmoid colon into the rectum. Then this distension of the rectal walls stimulates stretch receptors which results in defecation.
        
             
        
        
        
Uh the answer is B. Humans
        
             
        
        
        
I got two, but I could be wrong.
        
             
        
        
        
In homo sapiens(humans), males are the heterogametic sex meaning their sex chromosomes are not the same(=XY) while females are homogametic(=XX).
Sex linked traits or x linked traits are traits whose genes are present on the X chromosome. So if there is a recessive mutation in those genes, males will express that recessive trait. Basically males express everything that’s on their X chromosome because they only have 1, but females have 2 which helps “hide” the mutation and to not express the particular recessive trait. 
That is why sex linked traits are more evident in males in the population and an example of that would be colorblindness. 
Hope this helps:)