The correct answer is option B: soft, hard.

Explanation:
In woody plants, the bark is the protective outer covering of the stems, branches, and roots. It consists of several layers that provide protection against mechanical damage, pathogens, and environmental stresses. The bark is continuously produced by the cambium, a layer of meristematic cells located between the xylem and phloem tissues.

Early-season bark:
The bark formed early in the growing season is called "soft bark." This type of bark is characterized by its relatively low density and high moisture content. Soft bark is often smooth and pliable, and it can be easily peeled or scraped off.

Reasons for soft bark formation:
1. Rapid growth: During the early part of the growing season, plants experience rapid growth, resulting in the formation of new bark. This new bark is still immature and has not yet fully developed its protective characteristics.
2. High water content: Soft bark has a higher water content compared to mature bark. This moisture helps to keep the growing tissues hydrated and flexible.

End-of-season bark:
The bark formed towards the end of the growing season is called "hard bark." This type of bark is denser and more rigid than soft bark. It provides greater protection to the underlying tissues.

Reasons for hard bark formation:
1. Maturation: As the growing season progresses, the bark undergoes a process of maturation. The cells in the bark become thicker and more compact, resulting in a denser and harder structure.
2. Lignification: Lignin, a complex polymer, is deposited in the cell walls of the bark cells. This lignification process adds strength and rigidity to the bark, making it more resistant to damage.

Significance of bark types:
The transition from soft bark to hard bark is an important adaptation for woody plants. Hard bark provides increased protection against mechanical injuries, herbivory, and pathogens. It also helps to reduce water loss and prevent desiccation during periods of drought or cold temperatures.

In conclusion, the bark formed early in the season is called soft bark, while the bark formed towards the end of the season is called hard bark. This transition from soft to hard bark is an important adaptation for woody plants, providing increased protection and resilience.