This is an example of thigmotropism I believe.
The answer to this question is choice A, cell structure.
If two forces act on an object in the same direction, the net force is equal to the sum of the two forces. This always results in a stronger force than either of the individual forces alone.
The correct answers are:
d. Although most mammals, including humans, are not able to digest the milk sugar, lactose, after infancy, the ancestors of northern and western Europeans relied on dairy products as an important part of their food supply;
e. When other food sources were in low supply, mutations that allowed the expression of the enzyme lactase to persist past childhood conveyed an advantage to adults who were able to include dairy products in their diet.;
The humans from Northern and Western Europe, unlike the other people, lived in conditions where very often the food sources were scarce. With the domestication of the animals, especially the cows, goats, and sheep, the humans in this regions started to use the milk from these animals in times of crises. Over time their organisms started to become more prone to digesting the milk, thus having less and less problems with the lactose. Also, the people who were able to tolerate the dairy diet were seen as having advantageous traits, thus became more favorable for mating, which gradually increased and made dominant the population that is able to have dairy diet.
The public health measures that are most effective against pathogens transmitted through common vehicles are the water purification and food safety regulations. The most common vehicles or modes of transmission of infectious pathogens includes water, food, air, or the blood during transfusion. Ensuring use and supply of clean water and also safety food regulations may reduce the spread and transmission of disease causing pathogens.
