PLEASE HELP
An urban ecosystem is a designed ecosystem. Which of the following is (are) another example(s) of a designed ecosystem?
a. natural pond
b. a farm that has not been maintained for 10 years
c. fish aquarium
d. all of the above
16. Which of the following is an advantage of a synthetic fertilizer?
a. Amounts of nutrients can be precisely measured
b. Nutrients are lost from the soil through leaching
c. Benefits natural nutrient cycling
d. Less danger of overfertilizing