Choose the correct statement

Options

A. All mammals are viviparous
B. All cyclostomes do not possess jaws and paired fins
C. All reptiles have a three-chambered heart
D. All pisces have gills covered by an operculum

Answer

To solve the question "Choose the correct statement," we will analyze each statement provided and determine its accuracy.

### Step 1: Analyze the first statement
**Statement:** All mammals are viviparous.
**Analysis:** Viviparous means giving birth to live young rather than laying eggs. While most mammals are indeed viviparous, there are exceptions like the duck-billed platypus and echidna, which lay eggs.
**Conclusion:** This statement is incorrect.

**Hint:** Remember that while most mammals give birth to live young, there are exceptions in the form of egg-laying mammals.

### Step 2: Analyze the second statement
**Statement:** All cyclostomes do not possess jaws.
**Analysis:** Cyclostomes, which include lampreys and hagfish, are indeed jawless vertebrates. They are classified under the group Agnatha, which means "without jaws."
**Conclusion:** This statement is correct.

**Hint:** Focus on the classification of cyclostomes and their defining characteristics.

### Step 3: Analyze the third statement
**Statement:** All reptiles have a three-chambered heart.
**Analysis:** Most reptiles have a three-chambered heart, but crocodiles are an exception as they possess a four-chambered heart.
**Conclusion:** This statement is incorrect.

**Hint:** Consider the heart structure of reptiles and remember the notable exception of crocodiles.

### Step 4: Analyze the fourth statement
**Statement:** All Pisces (fishes) have gills covered by operculum.
**Analysis:** While bony fishes (Osteichthyes) have gills covered by an operculum, cartilaginous fishes (Chondrichthyes), such as sharks and rays, do not have an operculum.
**Conclusion:** This statement is incorrect.

**Hint:** Differentiate between the two major groups of fishes and their anatomical features.

### Final Conclusion
After analyzing all the statements, the only correct statement is: **All cyclostomes do not possess jaws.**

**Correct Answer:** Option 2 - All cyclostomes do not possess jaws.