In dicot stem

Options

A. The xylemis exarch
B. The xylem and phloem occur in separate bundles
C. Vascular bundles are arranged in a ring and have cambium
D. Vascular bundles are scattered and lack cambium

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of Dicot Stem**:
- Dicot stems are characterized by the arrangement of vascular bundles. They typically have a ring-like arrangement of vascular bundles.

2. **Identifying Vascular Bundles**:
- In dicot stems, the vascular bundles are arranged in a ring. Each vascular bundle consists of xylem and phloem.

3. **Types of Vascular Bundles**:
- The vascular bundles in dicot stems are described as "collateral" and "conjoint." This means that the xylem and phloem are located together in each bundle, with the xylem positioned towards the center and the phloem towards the outside.

4. **Presence of Cambium**:
- The vascular bundles in dicot stems are "open," which indicates that they contain cambium. Cambium is a layer of tissue that allows for secondary growth.

5. **Arrangement of Xylem and Phloem**:
- In the vascular bundles, the xylem is located on the inner side (centrifugally) and the phloem is on the outer side. This arrangement is referred to as "endarch."

6. **Evaluating the Options**:
- Now, let's evaluate the options provided:
- **Option 1**: "The xylem is exact" - This is incorrect as the xylem is not in an exact arrangement.
- **Option 2**: "The xylem and phloem occur in separate bundles" - This is also incorrect since they are found together in the same bundle.
- **Option 3**: "Vascular bundles are arranged in a ring and have cambium" - This is correct as described above.
- **Option 4**: "Vascular bundles scattered and lack cambium" - This is incorrect since the bundles are not scattered and do have cambium.

7. **Conclusion**:
- The correct answer is **Option 3**: "Vascular bundles are arranged in a ring and have cambium."