Select the correct statement from the following

Options

A. A mere 0.1% impurities cannot make domestic sewage unfit for human use
B. High concentrations of DDt disturb calcium metabolism in birds
C. Phaeophytization in lichens is caused due to nitrogen oxides
D. Bad' ozone as well as 'good' ozone both are found in the upper part of the atmosphere.

Answer

To solve the question "Select the correct statement from the following," we will analyze each statement provided in the question step by step.

### Step 1: Analyze the First Statement
The first statement claims that "a mere 0.1% impurities cannot make domestic sewage unfit for human use."

- **Evaluation**: Even a small percentage of impurities (like 0.01% or 0.1%) can significantly affect the quality of water and make it unfit for human consumption. Thus, this statement is **incorrect**.

### Step 2: Analyze the Second Statement
The second statement says, "high concentration of DDT disturb calcium metabolism in birds."

- **Evaluation**: DDT (Dichloro-Diphenyl-Trichloroethane) is a pesticide known to interfere with calcium metabolism in birds, leading to issues such as eggshell thinning. Therefore, this statement is **correct**.

### Step 3: Analyze the Third Statement
The third statement mentions, "Pheophytization in lichens is caused due to nitrogen oxide."

- **Evaluation**: Pheophytization, which refers to the process of chlorophyll breakdown in lichens, is primarily caused by sulfur oxides, not nitrogen oxides. Hence, this statement is **incorrect**.

### Step 4: Analyze the Fourth Statement
The fourth statement states, "bad zone as well as good zone both are found in the upper part of the atmosphere."

- **Evaluation**: The "bad zone" (where harmful pollutants are present) and the "good zone" (where beneficial ozone exists) are not both found in the upper atmosphere. This statement is also **incorrect**.

### Conclusion
After evaluating all the statements, the only correct statement is the second one: "high concentration of DDT disturb calcium metabolism in birds."

### Final Answer
The correct statement is: **High concentration of DDT disturb calcium metabolism in birds.**

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