Step 1: Understanding the Question:
This question tests knowledge of shifting cultivation and its sustainability.
Step 2: Detailed Explanation:
Shifting cultivation (slash and burn) was initially a low-input, sustainable system.
Now, it is not sustainable due to a decrease in the gestation period (fallow period).
The fallow period has decreased from 20-30 years to 5-10 years.
This leads to soil degradation and erosion.
Statement B says "drastic increase in the gestation period" which is incorrect.
Thus, statement B is NOT correct.
Step 3: Final Answer:
Thus, the incorrect statement is (B), which corresponds to option (B).
[0.5cm]