Mark the incorrectly matched pair:

Options

A. Petromyzon - Body devoid of scales and paired fins
B. Scoliodon - Operculum present but air bladder is absent
C. Exocoehis - Heart two chambered
D. Rona - Cold blooded with 2 pairs of limbs

Answer

To determine the incorrectly matched pair from the options provided, we will analyze each option step by step.

### Step 1: Analyze Option A - Petromycin
- **Classification**: Petromycin belongs to the class Cyclostomata.
- **Characteristics**: They are ectoparasites on some fishes, meaning they live on the outside of their host. They lack scales and paired fins, and have a circular mouth without jaws.
- **Conclusion**: This option is correctly matched.

### Step 2: Analyze Option B - Scoliodon
- **Classification**: Scoliodon belongs to the class Chondrichthyes.
- **Characteristics**: It is noted that Scoliodon has an operculum present and an air bladder absent. However, in reality, Scoliodon (a type of shark) does not have an operculum; it has gill slits instead. Additionally, it indeed lacks an air bladder.
- **Conclusion**: This option is incorrectly matched because it states that an operculum is present.

### Step 3: Analyze Option C - Exoskeletons
- **Classification**: Exoskeletons belong to class Osteichthyes.
- **Characteristics**: Osteichthyes are characterized by having a bony endoskeleton and typically have a two-chambered heart (one auricle and one ventricle).
- **Conclusion**: This option is correctly matched.

### Step 4: Analyze Option D - Rana
- **Classification**: Rana belongs to the class Amphibia.
- **Characteristics**: They are cold-blooded animals and possess two pairs of limbs.
- **Conclusion**: This option is correctly matched.

### Final Conclusion
After analyzing all options, the incorrectly matched pair is **Option B: Scoliodon**, as it incorrectly states that Scoliodon has an operculum.

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