Which one of the following did experiments with pea plants and found that pea plant has some traits which come in pairs - such as rough or smooth, tall or short, yellow or green etc. ?

The correct answer is Gregor Johann Mendel.

Gregor Johann Mendel conducted landmark hybridization experiments with pea plants (Pisum sativum) in the mid-19th century. Through his experiments, he observed that pea plants possess contrasting pairs of traits, such as:

• Seed texture: rough or smooth
• Plant height: tall or short
• Seed color: yellow or green
• Pod shape: inflated or constricted

Based on these experiments, Mendel formulated the fundamental principles of inheritance, which earned him the title of the "Father of Modern Genetics."