Smooth muscles occur in

Options

A. Vein
B. Artery
C. Uterus
D. All the above .

Answer

### Step-by-Step Solution:

1. **Understanding Muscle Types**:
- Muscles in the human body are categorized into three main types: cardiac muscles, smooth muscles, and skeletal muscles.
- Cardiac muscles are found in the heart and are responsible for pumping blood. Skeletal muscles are attached to bones and facilitate voluntary movements.

2. **Identifying Smooth Muscles**:
- Smooth muscles are non-striped (non-striated) muscles that are found in various internal organs.
- They are involuntary muscles, meaning they operate without conscious control.

3. **Locations of Smooth Muscles**:
- Smooth muscles are located in the walls of hollow organs such as:
- The esophagus (helps in the movement of food through peristalsis)
- The uterus (involved in contractions during childbirth)
- Blood vessels (arteries and veins, which regulate blood flow by contracting and relaxing)

4. **Characteristics of Smooth Muscles**:
- Smooth muscle fibers are smooth in appearance, have tapered ends, and contain a centrally located oval nucleus.
- Unlike skeletal muscles, they do not have visible stripes.

5. **Conclusion**:
- Based on the above information, smooth muscles occur in various internal organs (viscera) of the body, making option number four the correct answer.