The answer is B.
Water in the form of vapor enter the atmosphere. The vapor accumulates in the atmosphere to form clouds. Once the clouds are heavy enough, the water in the form of droplets fall towards land or as rain. It could also be in the form of other precipitation such as snow or hail. As the sun hits the waters in the land, it causes the water to evaporate and the cycle continues.
        
             
        
        
        
Answer: no body cavity—acoelomates; body cavity not completely lined with mesoderm—pseudocoelomates; body cavity completely lined with mesoderm—coelomates
 
        
             
        
        
        
Answer:
Even a slight reproductive advantage will eventually lead to the elimination of the less well adapted of two competing species
Explanation:
The competitive exclusion describes relationship between two species that compete for the limiting sources, and cannot coexist. It is enough for one species to have slightly advantage to be dominant over the other. As a consequence, other species (the weaker one) will be extincted (shift to a different ecological niche).