Haploid sexual spore produced exogenously is

Options

A. Ascospore
B. Basidiospore
C. Oospore
D. Zygospore

Answer

To answer the question "Haploid sexual spore produced exogenously is", we will go through the following steps:

### Step 1: Understand the Terms
- **Haploid**: This refers to a cell or organism that has a single set of chromosomes (n).
- **Sexual Spore**: This is a type of spore that is produced as a result of sexual reproduction, involving the fusion of gametes.
- **Exogenous**: This means that the spores are produced outside of a fruiting body or structure.

### Step 2: Identify the Types of Spores
- We need to consider the options provided: exospore, basidiospore, ospore, and ribospore.
- Each of these terms refers to different types of spores produced by various organisms, primarily fungi.

### Step 3: Analyze the Options
1. **Exospore**: Generally refers to spores that are produced externally but does not specifically denote haploid sexual spores.
2. **Basidiospore**: These are haploid spores produced by fungi in the class Basidiomycetes. They are formed on a structure called a basidium, and they are exogenously produced.
3. **Ospore**: This term is not commonly used in the context of fungi and does not refer to a recognized type of spore.
4. **Ribospore**: This term does not correspond to any known type of spore in biological classification.

### Step 4: Conclusion
- Based on the definitions and characteristics of the spores, the correct answer is **basidiospore**. Basidiospores are haploid, produced sexually, and are formed exogenously on the basidium of fungi belonging to the Basidiomycetes class.

### Final Answer
The haploid sexual spore produced exogenously is **basidiospore**.

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