Question

Which of the following units can be appropriately used in the expression of Primary Productivity of an ecosystem?

• A. g m²/yr
• B. Kg/Km²/yr
• C. g/yr
• D. g/m/yr

Hint:

Productivity = mass per unit area per unit time.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Pick the unit with dimension mass per area per time.

Step 2: Dimension check:
Needed: \(M\,L^{-2}\,T^{-1}\).

Step 3: Option 1:
\(M\,L^{2}\,T^{-1}\), area is in the wrong place. Fails.

Step 4: Option 2:
\(M\,L^{-2}\,T^{-1}\). Passes.

Step 5: Options 3 and 4:
\(M\,T^{-1}\) and \(M\,L^{-1}T^{-1}\). Both fail.

Step 6: Result:
Only option 2 has the right dimension, so it is the answer.

Quick Recap:
Recap: a productivity unit always has mass on top and area and time below. Dividing by area and time gives the rate per unit area per unit time, and only option 2 follows this rule.

Final Answer:
\[\boxed{2}\]