What is common in whale, bat and rat ?

Options

A. Absence of neck
B. Muscular diaphragm between thorax and abdomen
C. Testes, outside abdominal cavity
D. External earpinna

Answer

To determine what is common among a whale, bat, and rat, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Group**: First, we need to recognize that all three animals—whale, bat, and rat—belong to the class Mammalia. This means they share certain fundamental characteristics typical of mammals.

2. **Examine the Options**: Next, we should evaluate the given options to find a common trait:
- **Option 1: Absence of neck**: Check if all three animals lack a neck. However, all three do have necks, so this option is incorrect.
- **Option 2: Muscular diaphragm between thorax and abdomen**: This is a muscle that aids in breathing and is a characteristic feature of mammals. It separates the thoracic cavity from the abdominal cavity. Since all three animals possess a muscular diaphragm, this option is likely correct.
- **Option 3: Testis outside abdominal cavity**: In mammals, the testes are typically located outside the abdominal cavity. However, in whales, the testes are located inside the abdominal cavity, a condition known as cryptorchidism. Therefore, this option is not common to all three.
- **Option 4: External ear pinna**: The external ear pinna is present in bats and rats but absent in whales. Thus, this option is also incorrect.

3. **Conclusion**: After evaluating all the options, the only common characteristic among the whale, bat, and rat is the presence of a muscular diaphragm. Therefore, the answer is that they all have a muscular diaphragm between the thorax and abdomen.

### Final Answer:
The common characteristic in whale, bat, and rat is the presence of a muscular diaphragm between the thorax and abdomen.