How did Mendel make sure that the pea plants were true breeding?

Explanation

### Step-by-Step Solution:

1. **Understanding True Breeding Lines**:
- True breeding lines are those in which the plants consistently produce offspring with the same traits when self-fertilized. This means that the alleles for a particular trait are homozygous, meaning they are identical (e.g., TT for tall plants or tt for dwarf plants).

2. **Selection of Pea Plants**:
- Mendel selected specific pea plants that exhibited distinct traits, such as height (tall vs. dwarf). He ensured that these plants were pure by observing their characteristics over multiple generations.

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