Which of the following is an example of a concave structure

The definition of concave is to be curved inward. ... At the location of the fracture, we see the skull is curved inward, so we would say the skull is concave. Some other examples would be a dented can or car bumper. Whenever an object is curved inward, we say the object is concave.

there are no details given

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.