Lying outside the vascular cambium
The bark of a plant is the protective outer covering of the trunk, branches, and stems. It serves as a barrier against physical damage, pathogens, and excessive water loss. The bark includes all the tissues lying outside the vascular cambium, which is the layer of actively dividing cells responsible for secondary growth in plants.

Formed by vascular cambium
The vascular cambium is a meristematic tissue that produces secondary xylem (wood) towards the inside and secondary phloem (inner bark) towards the outside. The secondary phloem is a part of the bark, and it is responsible for transporting sugars and other organic compounds from the leaves to other parts of the plant.

Formed by phellogen
The phellogen, also known as the cork cambium, is a lateral meristem that produces cork cells towards the outside and phelloderm cells towards the inside. The cork cells, also known as phellem, are dead at maturity and form the outermost layer of the bark. They are impermeable to water and provide protection to the underlying tissues.

Phellem and phelloderm
Phellem is the outermost layer of the bark, composed of dead cork cells. It provides a waterproof barrier, preventing water loss and protecting the inner tissues from pathogens and mechanical damage. Phelloderm is the layer of living cells that forms towards the inside of the cork cambium. It is responsible for producing parenchyma cells and may have a role in wound healing.

Correct answer
The correct answer is option 'A', which states that the bark includes all the tissues lying outside the vascular cambium. This is because the bark is composed of the secondary phloem (inner bark), which is formed by the vascular cambium, as well as the outermost layer of dead cork cells (phellem) produced by the cork cambium. The phelloderm, which is also formed by the cork cambium, is not considered a part of the bark.