Scales in Osteichthyes are

Options

A. cycloid or ctenoid
B. placoid or cycloid
C. palcoid or ctenoid
D. all the above

Answer

To answer the question about the types of scales found in Osteichthyes (bony fishes), we can follow these steps:

### Step-by-Step Solution:

1. **Understand Osteichthyes**: Osteichthyes, commonly known as bony fishes, are characterized by having a skeleton made of bone rather than cartilage.

2. **Identify Types of Scales**: In Osteichthyes, there are three main types of scales:
- **Cosmoid Scales**
- **Ganoid Scales**
- **Teleost Scales**

3. **Focus on Teleosts**: The teleosts, which are a subgroup of Osteichthyes, are further divided into two types of scales:
- **Cycloid Scales**
- **Tenoid Scales**

4. **Differentiate from Chondrichthyes**: It is important to note that cartilaginous fishes (Chondrichthyes), such as sharks and rays, have **placoid scales**. These scales are not found in Osteichthyes.

5. **Evaluate the Options**: Given the options:
- Cycloid or Tenoid
- Placoid or Cycloid
- Placoid or Tenoid
- All of the above

We can eliminate the options that include placoid scales, as they are not present in Osteichthyes.

6. **Select the Correct Answer**: The only correct answer that pertains to the scales found in Osteichthyes is **Cycloid or Tenoid**.

### Final Answer:
The scales in Osteichthyes are **Cycloid or Tenoid**.

---