The total economic value of an ecosystem:

a. is composed of the direct values an ecosystem provides upon which a price can be placed, such as crops and medicinal plants.
b. is the monetary value of all of the services an ecosystem provides. includes all of the ecosystem services, future uses, and non-use values (such as cultural, intrinsic, and aesthetic values) of an ecosystem.
c. is composed of the utilized services and goods an ecosystem provides, such as water storage and filtration, even if they are not directly paid for.
d. is the monetary value of all of the services an ecosystem provides.
e. includes all of the ecosystem services, future uses, and non-use values (such as cultural, intrinsic, and aesthetic values) of an ecosystem.

b.is the monetary value of all of the services an ecosystem provides. includes all of the ecosystem services, future uses, and non-use values (such as cultural, intrinsic, and aesthetic values) of an ecosystem.

Explanation:

The total economic value of an ecosystem refers to all the services which are provided by an ecosystem that is used by now and in the future. Economic value is also refers to the analysis that how much cost is done on the services and how much profit be made from it. There are four terms used in economic value of an ecosystem i. e. Use value, non use value, option value and existence value.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.