Choose the correct Statement.

Options

A. 0.1% of impurities in sewage water also consist of suspended solids like fecal matter , bacteria , paper fibers , etc. .
B. Mauve-coloured flowers are a characteristic feature of the world's most problematic weed .
C. Algal blooms cause deterioration of the water quality but do not cause any harm to other aquatic life, like fish .
D. Biomagnification refers to the decrease in concentration of the toxicant at successive trophic levels .

Answer

To solve the question "Choose the correct Statement," we will analyze each of the four statements provided in the video transcript step by step.

### Step 1: Analyze the First Statement
The first statement discusses the composition of sewage water, specifically mentioning that 0.1% of impurities consists of suspended solids like fecal matter, bacteria, and fibers.

**Evaluation**:
- The statement is partially correct. While it is true that sewage water contains suspended solids, the examples given (fecal matter, bacteria, etc.) are more representative of colloidal materials rather than just suspended solids.

**Conclusion**: This statement is misleading and not entirely accurate.

### Step 2: Analyze the Second Statement
The second statement refers to a characteristic feature of a problematic weed, specifically mentioning its flower color.

**Evaluation**:
- The statement correctly identifies the flower color of the world's most problematic weed, which is indeed pale purple or lavender. This weed is known as water hyacinth, which is native to tropical and subtropical regions and is notorious for its rapid growth.

**Conclusion**: This statement is correct.

### Step 3: Analyze the Third Statement
The third statement claims that algal blooms cause deterioration of water quality but do not harm other aquatic life like fish.

**Evaluation**:
- This statement is incorrect. Algal blooms lead to a decrease in dissolved oxygen levels (DO) and an increase in Biochemical Oxygen Demand (BOD), which can harm aquatic life, including fish. The decomposition of organic matter due to algal blooms consumes oxygen, leading to hypoxic conditions that can be fatal for aquatic organisms.

**Conclusion**: This statement is false.

### Step 4: Analyze the Fourth Statement
The fourth statement discusses biomagnification, claiming it refers to the decrease in concentration of the toxicant at successive trophic levels.

**Evaluation**:
- This statement is incorrect. Biomagnification actually refers to the increase in concentration of toxic substances as one moves up the food chain. As organisms at lower trophic levels accumulate toxins, these toxins become more concentrated in the bodies of organisms at higher trophic levels.

**Conclusion**: This statement is false.

### Final Conclusion
After analyzing all four statements, the only correct statement is the second one, which describes the flower color of the world's most problematic weed, water hyacinth.