The word sponge is more appropriate to use than Underground river since an underground river can loose water while an aquifer cannot loose water, unless it is open-air and above ground. then the aquifer would slowly loose water due to evaporation from the sun.
Answer:
Declining crude birth rates.
Explanation:
Birth rate may be defined as the number of births takes place per year per thousand of the population. The birth rate and death rate may change the population dynamics.
The developing countries shows the expanding population graph as they have more number of people of the reproductive age. The advancement in the medical field results in the decline birth rate that causes the decline of the nature resources.
Thus, the answer is declining crude birth rates.
The answer is long
The bone indicated by the arrow is femur bone. It should be classified as the long bone. Other example for long bones would be tibia and fibula. Short bone would be carpal or tarsal bones. Flat bone could be found in skull. Irregular bone would be the vertebrae or pelvic.