Step 1: Understanding the Concept
Phosphorus has practically no gaseous form, unlike carbon.
Step 2: Statement I
Exchange of phosphorus between organisms and environment is slow and small, not very high.
So Statement I is incorrect.
Step 3: Statement II
Atmospheric input of phosphorus through rainfall is much smaller than that of carbon, not the other way round.
So Statement II is incorrect.
Final Answer:
Both statements are incorrect.
\[ \boxed{\text{(B) }\text{Both statement I and statement II are incorrect.}} \]