Which one of the following characteristics is common both in human and adult frogs?

Options

A. Nucleated RBCs
B. Ureotelic mode of excretion
C. Four-chambered heart
D. Internal fertilisation

Answer

To determine the common characteristic between humans and adult frogs, we need to analyze the options provided in the question:

1. **Nucleated RBCs**: Frogs have nucleated red blood cells (RBCs), while humans have enucleated RBCs. Therefore, this characteristic is not common.

2. **Ureotelic Mode of Excretion**: Both humans and adult frogs excrete urea as their primary nitrogenous waste product. Humans are ureotelic, and adult frogs also become ureotelic after metamorphosis from their tadpole stage.

3. **4-Chamber Heart**: Humans possess a 4-chambered heart, whereas frogs have a 3-chambered heart (two atria and one ventricle). Hence, this characteristic is not common.

4. **Internal Fertilization**: Humans undergo internal fertilization, while frogs typically exhibit external fertilization. Thus, this characteristic is also not common.

Based on this analysis, the common characteristic between humans and adult frogs is the **ureotelic mode of excretion**, as both excrete urea.

### Step-by-Step Solution:
1. **Identify the Options**: Look at the characteristics provided: nucleated RBCs, ureotelic mode of excretion, 4-chamber heart, and internal fertilization.

2. **Analyze Nucleated RBCs**: Determine that frogs have nucleated RBCs while humans do not, so this is not common.

3. **Evaluate Ureotelic Excretion**: Recognize that both humans and adult frogs excrete urea, making this a common characteristic.

4. **Check Heart Structure**: Understand that humans have a 4-chambered heart while frogs have a 3-chambered heart, so this is not common.

5. **Consider Fertilization Type**: Note that humans have internal fertilization and frogs have external fertilization, which means this is not common.

6. **Conclude**: Based on the analysis, conclude that the common characteristic is the ureotelic mode of excretion.