Different respiratory organs are present in different organisms. X is the main respiratory organ in humans. Respiratory system of cockroach consists of small openings on the sides of its body called tracheoles which are connected to the tubes called tracheae that are further branched into spiracles. Scoliodon respires through y which is richly supplied with blood vessels. Z is the main site of gaseous exchange in plants. Each Z is guarded by two kidney shaped subsidiary cells which are further flanked by specialised epidermal cells called guard cells.
Identify X, Y and Z in the given passage and select the incorrect option regarding them.

Options

A. Whales and dolphins also have X as their respiratory organ where alveoli is the main site of gaseous exchange.
B. Y is the respiratory organ in tadpole larva and sea horse.
C. Z is absent in all hydrophytes but is abundantly present on the upper leaf surface of all xerophytes.
D. When pressure inside X drops, inspiration occurs and when pressure inside X starts increasing the air contained in it is pushed out causing expiration.

Explanation

To solve the question, we need to identify the respiratory organs X, Y, and Z based on the descriptions provided in the passage.

### Step-by-Step Solution:

1. **Identify X**:
- The passage states that "X is the main respiratory organ in humans."
- The main respiratory organ in humans is the **lungs**.
- Therefore, **X = Lungs**.

2. **Identify Y**:
- The passage mentions that "Scoliodon respires through Y which is richly supplied with blood vessels."
- Scoliodon is a type of shark, and sharks respire through **gills**.
- Therefore, **Y = Gills**.

3. **Identify Z**:
- The passage states that "Z is the main site of gaseous exchange in plants" and that "each Z is guarded by two kidney-shaped subsidiary cells which are further flanked by specialized epidermal cells called guard cells."
- The main site of gaseous exchange in plants is the **stomata**.
- Therefore, **Z = Stomata**.

4. **Select the Incorrect Option**:
- Now we need to evaluate the options provided regarding X, Y, and Z to find the incorrect statement.
- From the video transcript, we learn that the incorrect statement is: "Z is absent in all hydrophytes, but is present on the upper leaves." This is incorrect because stomata can be present in hydrophytes, but they may be less prominent or absent in submerged aquatic plants.

### Final Answer:
- **X = Lungs**
- **Y = Gills**
- **Z = Stomata**
- The incorrect option is the one stating that "Z is absent in all hydrophytes, but is present on the upper leaves."