Choose the incorrect statement :

Options

A. We are encouraged to plant more trees so as to ensure clean environment and also provide biomass fuel.
B. Gober gas is produced when crops, vegetable wastes, etc., decompose in the absence of oxygen.
C. The main ingredient of biogas is ethane and it gives a lot of smoke and also produces a lot of residual ash.
D. Biomass is a renewable source of energy.

Explanation

To determine the incorrect statement from the provided options, let's analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** "We are encouraged to plant more trees so as to ensure a clean environment and also provide biomass fuel."
- **Analysis:** This statement is correct. Trees help in cleaning the environment by absorbing carbon dioxide and releasing oxygen. They also provide biomass fuel, which is derived from organic matter.

### Step 2: Analyze the second statement
**Statement:** "Gober gas is produced when crops, vegetables, etc. decompose in the absence of oxygen."
- **Analysis:** This statement is also correct. Gober gas (or biogas) is produced from the anaerobic decomposition of organic matter, such as cow dung, in the absence of oxygen.

### Step 3: Analyze the third statement
**Statement:** "The main ingredient of biogas is ethane and it gives a lot of smoke and produces a lot of residual ash."
- **Analysis:** This statement is incorrect. The main ingredient of biogas is methane, not ethane. Additionally, biogas does not produce a lot of smoke or residual ash when burned, which is a characteristic of cleaner fuels.

### Step 4: Analyze the fourth statement
**Statement:** "Biomass is a renewable source of energy."
- **Analysis:** This statement is correct. Biomass, which consists of dead organic matter from plants and animals, is indeed a renewable source of energy.

### Conclusion
The incorrect statement is: "The main ingredient of biogas is ethane and it gives a lot of smoke and produces a lot of residual ash."

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