Which of the following pair of contrasting traits was not studied by Mendel?

The correct option is Pink and white flowers.

Gregor Mendel, known as the father of modern genetics, conducted hybridization experiments on garden pea plants (Pisum sativum). During his research, he selected and studied seven pairs of contrasting traits to understand the laws of inheritance.

Let's review the seven pairs of contrasting characters studied by Mendel:
1. Stem height: Tall vs. Dwarf
2. Flower color: Violet vs. White (often referred to as Purple vs. White)
3. Flower position: Axial vs. Terminal
4. Pod shape: Inflated vs. Constricted
5. Pod color: Green vs. Yellow
6. Seed shape: Round vs. Wrinkled
7. Seed color: Yellow vs. Green

By comparing the options with Mendel's studied traits:
- "Inflated and constricted pods" is a studied trait (Pod shape).
- "Axial and terminal flowers" is a studied trait (Flower position).
- "Green and yellow pods" is a studied trait (Pod color).
- "Pink and white flowers" is not a pair of traits studied by Mendel. The flower color traits he studied were violet (or purple) and white.

Therefore, pink and white flowers was not among the contrasting traits studied by Mendel.