O2 (oxygen) is a covalent compound
Answer is A. I kid chemistry a while back but I am pretty certain it is A.
Answer:
During the summer months, the water table tends to fall, due in part to plants taking up water from the soil surface before it can reach the water table. The water table level is also influenced by human extraction of groundwater using wells; groundwater is pumped out for drinking water and to irrigate farmland.
Explanation:
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.