Which of the following contributed to the success of Mendel?

Options

A. Qualitative analysis of data
B. Observation of distinct inherited traits
C. His knowledge of Biology
D. Consideration of one character at one time

Explanation

To solve the question regarding the factors that contributed to the success of Gregor Mendel in his experiments with inheritance, we can analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understand Mendel's Work**: Gregor Mendel is known as the father of genetics due to his pioneering work with pea plants. He established the basic principles of heredity through his experiments.

2. **Evaluate Each Option**:
- **Option 1: Qualitative analysis of data**: While Mendel did analyze data, his success was not primarily due to qualitative analysis. This option is incorrect.
- **Option 2: Observation of distinct inherited traits**: Mendel focused on specific traits that were easily observable, such as flower color and seed shape. However, this alone does not encompass the entirety of his success. This option is also incorrect.
- **Option 3: His knowledge of biology**: Although Mendel had a solid understanding of biology, it was his methodological approach that truly set his work apart. Thus, this option is incorrect.
- **Option 4: Consideration of one character at one time**: This is a key aspect of Mendel's methodology. By focusing on one trait at a time, he was able to clearly observe patterns of inheritance. This approach allowed him to formulate his laws of inheritance effectively. This option is correct.

3. **Conclusion**: The factor that most significantly contributed to Mendel's success was his consideration of one character at one time. Therefore, the correct answer is **Option 4**.

### Final Answer:
The correct option that contributed to the success of Mendel is **Option 4: Consideration of one character at one time**.