Step 1: Understanding the Concept
Ecosystem services are the products and processes of healthy ecosystems that people receive free of cost.
Step 2: Examples
Purification of air and water, pollination, soil formation, nutrient cycling, climate regulation and flood control.
Step 3: Select
They are benefits and not harmful effects, artificial inputs or pollutants.
Final Answer:
Ecosystem services are the benefits humans obtain from ecosystems.
\[ \boxed{\text{(B) }\text{Benefits humans obtain from ecosystems}} \]