Sac fungi which contaminate culture media and is also referred as ''laboratory weed'' is :

Options

A. Claviceps purpurea
B. Aspergillus niger
C. Neurospora crassa
D. Penicillium chrysogenum

Answer

To solve the question about the sac fungi that contaminate culture media and is referred to as "laboratory weed," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for a specific type of sac fungi that is known to contaminate culture media and is commonly referred to as a "laboratory weed."

2. **Identify the Options**: The options provided are:
- A) Claviceps purpurea
- B) Aspergillus niger
- C) Neurospora crassa
- D) Penicillium chrysogenum

3. **Analyze Each Option**:
- **Option A: Claviceps purpurea** - This is known as the ergot fungus, which grows on rye and is not typically associated with laboratory contamination.
- **Option B: Aspergillus niger** - This is a type of sac fungi that is indeed known to contaminate culture media and is often referred to as a "laboratory weed."
- **Option C: Neurospora crassa** - This is a type of bread mold, not a sac fungus that contaminates culture media.
- **Option D: Penicillium chrysogenum** - While this fungus is important in antibiotic production, it is not classified as a sac fungus and does not fit the description in the question.

4. **Select the Correct Answer**: Based on the analysis, the correct answer is **B) Aspergillus niger**. It is the sac fungus that contaminates culture media and is referred to as a "laboratory weed."

### Final Answer:
The sac fungi which contaminate culture media and is also referred to as "laboratory weed" is **Aspergillus niger**.

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