The teaching material should be in accordance with the mental age and should have relevance in real life situations. It is main characteristic of:

Question

Accepted Answer

The correct answer to the question is Option 1: Principles of Selection. Let's delve into why this is the correct choice and why the other options are not suitable.

1. **Principles of Selection**:
   - The Principles of Selection emphasize choosing teaching materials that align with the learners' mental age and have practical relevance to real-life situations. This principle ensures that the content is appropriate for the cognitive development stage of the learners, making it more engaging and effective. By selecting materials that resonate with students' real-world experiences, educators can facilitate better understanding and retention of knowledge. This approach is crucial in creating a meaningful and applicable learning experience, which is why it is identified as the main characteristic in the question.

2. **Principles of Habit Formation**:
   - The Principles of Habit Formation focus on creating consistent and repetitive learning experiences to instill habits in learners. While important for developing routine skills and behaviors, this principle does not specifically address the alignment of teaching materials with mental age or real-life relevance. Therefore, it is not the correct answer for the question posed.

3. **Principles of Gradation**:
   - The Principles of Gradation involve organizing learning materials in a sequence that progresses from simple to complex. This principle is concerned with the order and difficulty level of content rather than its relevance to mental age or real-life situations. Although gradation is essential for structured learning, it does not directly address the main characteristic highlighted in the question.

4. **Principles of Controlled Vocabulary**:
   - The Principles of Controlled Vocabulary pertain to the use of a specific set of terms to ensure clarity and consistency in communication. This principle is particularly relevant in language learning and technical subjects but does not relate to the selection of teaching materials based on mental age or real-life applicability. Hence, it is not the correct answer for the given question.

In conclusion, Option 1: Principles of Selection is the correct answer because it directly addresses the need for teaching materials to be suitable for the learners' mental age and relevant to real-life situations, ensuring an effective and meaningful educational experience.