The term bark refers to
(a) periderm and secondary phloem only
(b) periderm , secondary phloem and vascular cambium only
(c) secondary xylem and cambium only
(d) periderm only

Options

A. primary and secondary phloem only
B. periderm , secondary phloem and vascular cambium only
C. secondary xylem and cambium only
D. periderm only.

Answer

To determine what the term "bark" refers to, we need to analyze the options given in the question and understand the components that make up bark in plants.

### Step-by-Step Solution:

1. **Understanding Bark**:
- The term "bark" refers to all the tissues outside the vascular cambium in a plant. This includes various layers that contribute to the protective outer covering of the plant.

2. **Identifying Components of Bark**:
- The bark is primarily composed of:
- **Periderm**: This is the outer protective layer and consists of:
- **Cork**: The outermost layer that provides protection.
- **Cork Cambium**: The layer that produces cork cells.
- **Secondary Cortex**: The layer beneath the cork.
- **Secondary Phloem**: This is the inner layer that is responsible for the transport of nutrients.

3. **Evaluating the Options**:
- **Option (a)**: Periderm and secondary phloem only.
- This option includes the main components of bark but does not mention vascular cambium, which is not part of the bark.
- **Option (b)**: Periderm, secondary phloem, and vascular cambium only.
- This option incorrectly includes vascular cambium, which is not part of the bark.
- **Option (c)**: Secondary xylem and cambium only.
- This option is incorrect as it does not include any of the bark components.
- **Option (d)**: Periderm only.
- This option is incomplete as it does not include secondary phloem.

4. **Conclusion**:
- The correct answer is **(a) periderm and secondary phloem only**. This option accurately reflects the components that make up the bark.

### Final Answer:
(a) periderm and secondary phloem only