Dengue fever, a zoonotic disease, is endemic in northern mexico, but not in the u. s. provide two possible explanations for this dichotomy and explain your answer.

One explanation could be the differences in climate (environmental factors). The climate in northern Mexico could support the reproduction of the mosquito species, which is a vector of the dengue virus.   Other environmental conditions that influence its endemicity could include living conditions and sanitation. The other possiblity could be that the people in the US have developed immunity for the disease, therefore, are unaffected even when infected by the virus.

weathering is the answer.

it cools slower in the earth meaning the crystals have more time to form than lava on the surface