Which one of the following is a plant hormone used to regulate growth, cell division, and various developmental processes in plants?

Introduction / Context:
Plant hormones, also called phytohormones, are chemical substances that control growth, development, and responses to the environment in plants. Examinations in biology and general knowledge often ask you to distinguish plant hormones from animal hormones. This question checks whether you can identify a plant specific hormone, cytokinin, among a group of commonly known animal hormones. Correctly recognizing cytokinin shows that you understand basic plant physiology terminology.

Given Data / Assumptions:
The stem asks for a plant hormone that regulates growth and cell division. The options list Oestrogen, Insulin, Cytokinin, Thyroxin, and Adrenaline. We assume the learner knows that most of these hormones belong to animal or human endocrine systems. Only one option is a classic example of a plant hormone involved in cell division and shoot formation. The question is a straightforward recall type question if you know the standard list of plant hormones.

Concept / Approach:
Major plant hormones include auxins, gibberellins, cytokinins, ethylene, and abscisic acid. Cytokinins are known for stimulating cell division, delaying leaf senescence, and promoting shoot formation in tissue culture. The other options, such as Oestrogen, Insulin, Thyroxin, and Adrenaline, are all vertebrate or human hormones with no hormonal role in plants. Therefore, the correct approach is to recall the names of plant hormones and pick the one that belongs to that group. This makes cytokinin the only appropriate answer.

Step-by-Step Solution:
Step 1: Recall the common plant hormones: auxin, gibberellin, cytokinin, ethylene, and abscisic acid.Step 2: Read each option and identify whether it is known as a plant or animal hormone.Step 3: Recognize that Oestrogen, Insulin, Thyroxin, and Adrenaline are all well known animal hormones.Step 4: Note that cytokinin is a phytohormone involved in cell division and growth in plants.Step 5: Choose the option that names cytokinin as a plant growth regulating hormone.

Verification / Alternative check:
To verify, you can recall plant tissue culture experiments where cytokinins and auxins are used in combination to regulate shoot and root formation. When the cytokinin concentration is higher, shoot formation is promoted, which confirms its role in cell division and growth. None of the other hormones are used in such plant culture experiments because they belong to animal physiology. This practical memory confirms that cytokinin is indeed the plant hormone among the options.

Why Other Options Are Wrong:
Oestrogen is a female sex hormone in humans and other mammals and plays no hormonal role in plants. Insulin is a peptide hormone secreted by the pancreas in animals to regulate blood glucose levels. Thyroxin is a thyroid hormone that controls metabolic rate in vertebrates. Adrenaline, also called epinephrine, is secreted by the adrenal medulla and prepares the body for fight or flight responses. Since all of these hormones belong to animal endocrine systems, they cannot be considered plant hormones.

Common Pitfalls:
Students sometimes answer incorrectly because they see familiar names like Insulin or Thyroxin and think the question is about general hormones rather than plant hormones. Another pitfall is forgetting the names of less commonly mentioned plant hormones beyond auxin. To avoid these mistakes, memorize at least the main plant hormone names and associate cytokinin specifically with cell division and shoot growth. This will make such exam questions quick and easy to answer.

Final Answer:
The plant hormone among the options is Cytokinin, a plant growth regulating hormone.