Mendal selected.

Options

A. 7 true-breeding pea plant varieties
B. 14 true-breeding pea plant varieties
C. 21 true-breeding pea plant varieties
D. 28 true-breeding pea plant varieties

Answer

### Step-by-Step Solution:

1. **Understanding Mendel's Experiment**: Gregor Mendel is known as the father of genetics. He conducted experiments on pea plants (Pisum sativum) to study inheritance patterns.

2. **Selection of True Breeding Lines**: Mendel selected 14 true breeding pea plant lines. True breeding means that the plants, when self-fertilized, will produce offspring that are identical to themselves for a particular trait.

3. **Traits Studied by Mendel**: Mendel focused on several traits in pea plants, each with two variations:
- **Stem Height**: Tall (dominant) and Dwarf (recessive)
- **Flower Color**: Purple (dominant) and White (recessive)
- **Flower Position**: Axial (dominant) and Terminal (recessive)
- **Pod Shape**: Inflated (dominant) and Constricted (recessive)
- **Pod Color**: Green (dominant) and Yellow (recessive)
- **Seed Shape**: Round (dominant) and Wrinkled (recessive)
- **Seed Color**: Yellow (dominant) and Green (recessive)

4. **Total Traits**: Mendel studied seven traits in total, each with two variations. However, the mention of "14 true breeding lines" indicates that he selected different combinations of these traits.

5. **Conclusion**: Mendel's selection of 14 true breeding lines allowed him to conduct his experiments effectively, leading to the formulation of the fundamental laws of inheritance.