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. Exocoetus - Heart two chamered with sinus venosus
D. Rana - Cold blooded with 10 pairs of cranial nerves and mesonephric kidneys

Answer

To solve the question of identifying the incorrectly matched pair, we will analyze each option provided in the question step by step.

### Step 1: Analyze the first option - Patromyzone
- **Description**: Patromyzone is matched with "body divided into scales and paired fins."
- **Analysis**: Patromyzone, also known as lampreys, belong to a group of jawless fish. They do not have scales and lack paired fins. Therefore, this match is incorrect.

### Step 2: Analyze the second option - Squalidon
- **Description**: Squalidon is matched with "operculum present but ear bladder absent."
- **Analysis**: Squalidon is a type of cartilaginous fish (related to sharks). Cartilaginous fish do not have an operculum; this structure is found in bony fish. Therefore, this match is also incorrect.

### Step 3: Analyze the third option - Exocetus
- **Description**: Exocetus is matched with "a heart with two chambers and sinus venosus."
- **Analysis**: Exocetus, commonly known as flying fish, has a heart with two chambers (like all bony fish) and possesses a sinus venosus. This match is correct.

### Step 4: Analyze the fourth option - Rana
- **Description**: Rana is matched with "cold-blooded with 10 pairs of cranial nerves and mesonephric kidneys."
- **Analysis**: Rana, which includes frogs, is indeed cold-blooded and has 10 pairs of cranial nerves along with mesonephric kidneys. This match is correct.

### Conclusion
After analyzing all the options, we find that the incorrectly matched pairs are:
1. Patromyzone - Incorrectly matched with scales and paired fins.
2. Squalidon - Incorrectly matched with operculum present.

However, since the question asks for one incorrectly matched pair, the most clear and definitive incorrect match is **Squalidon**.

### Final Answer
The incorrectly matched pair is **Squalidon** with "operculum present but ear bladder absent."

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