Which of the following is an example of hybrid vigour?

Options

A. mule
B. donkey
C. horse
D. neoplina

Answer

### Step-by-Step Solution:

1. **Understanding Hybrid Vigour**:
- Hybrid vigour, also known as heterosis, refers to the phenomenon where the offspring (hybrids) exhibit improved or superior qualities compared to their parents. This often occurs when two different species or varieties are crossed.

2. **Analyzing the Options**:
- The options given are:
- a) Mule
- b) Donkey
- c) Horse
- d) Neoplena

3. **Identifying the Hybrid**:
- A mule is a hybrid that results from the mating of a male donkey (jack) and a female horse (mare). This crossbreeding results in an offspring that inherits desirable traits from both parent species.

4. **Evaluating Other Options**:
- Donkey: This is not a hybrid; it is a species on its own.
- Horse: This is also a species and not a hybrid.
- Neoplena: This is not a commonly recognized term in the context of hybrid vigour.

5. **Conclusion**:
- Since the mule is the only option that results from the hybridization of two different species (donkey and horse), it exemplifies hybrid vigour. Therefore, the correct answer is **option a) Mule**.