(a) Essential elements are components of energy related compounds
(b) Essential elements are components of structural elements of cells.
(c ) `Mn^(2 + ) ` is an activator of alcohol dehydrogenase

Options

A. All are correct
B. Only (a) is incorrect
C. Only (b) is incorrect
D. Only (c ) is incorrect

Answer

To solve the question, we need to evaluate each of the three statements regarding essential elements in the context of mineral nutrition.

### Step-by-Step Solution:

1. **Evaluate Statement (a)**:
- The statement claims that essential elements are components of energy-related compounds.
- Essential elements, particularly macronutrients like phosphorus (P) and magnesium (Mg), are indeed components of energy-related compounds. For example, phosphorus is a key component of ATP (adenosine triphosphate), which is the primary energy carrier in cells. Magnesium is a part of chlorophyll, which is essential for photosynthesis, a process that converts light energy into chemical energy.
- **Conclusion**: Statement (a) is **correct**.

2. **Evaluate Statement (b)**:
- This statement asserts that essential elements are components of structural elements of cells.
- Essential elements such as carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) are indeed fundamental components of the structural elements of cells. They are the building blocks of macromolecules like carbohydrates, proteins, and nucleic acids, which make up the structure of cells.
- **Conclusion**: Statement (b) is **correct**.

3. **Evaluate Statement (c)**:
- The statement claims that `Mn^(2+)` (manganese) is an activator of alcohol dehydrogenase.
- This statement is **incorrect**. Alcohol dehydrogenase is actually activated by zinc ions (`Zn^(2+)`), not manganese ions. Manganese does play a role in other enzymatic processes, but it is not the activator for alcohol dehydrogenase.
- **Conclusion**: Statement (c) is **incorrect**.

### Final Conclusion:
- Statements (a) and (b) are correct, while statement (c) is incorrect.