Pinnae are present in

Options

A. monotremes
B. cetaceans
C. sirenians
D. marsupials

Answer

To determine where pinnae are present among the given options (monotremes, cetaceans, serenian, or marsupials), we can break down the characteristics of each group step by step:

### Step 1: Understand what pinnae are
Pinnae refer to the external part of the ear, which is visible and helps in collecting sound.

**Hint:** Remember that pinnae are the outer ear structures that help in sound collection.

### Step 2: Analyze monotremes
Monotremes are a group of egg-laying mammals, such as the platypus and echidna. They do not have external ears (pinnae).

**Hint:** Think about the reproductive method of monotremes and their ear structure.

### Step 3: Analyze cetaceans
Cetaceans include aquatic mammals like whales and dolphins. They are adapted to life in water and do not have external ears.

**Hint:** Consider how cetaceans are adapted to their aquatic environment and their ear structure.

### Step 4: Analyze serenian
Serenians, such as sea cows (manatees), are also aquatic mammals. They are herbivorous and inhabit rivers and swamps, but they too lack external ears.

**Hint:** Reflect on the habitat and characteristics of serenian mammals.

### Step 5: Analyze marsupials
Marsupials, like kangaroos, are mammals that carry their young in pouches. They possess external ears (pinnae), which are visible and functional.

**Hint:** Think about the common characteristics of marsupials and their reproductive methods.

### Conclusion
Based on the analysis, pinnae are present in marsupials.

**Final Answer:** Pinnae are present in marsupials.