Question: In the 17th century, Gregor Mendel crossed pea plants with different traits and observed the results in their offspring. To which of these did Mendel contribute most directly with his work?

What is the correct answer to the question from the following choices?
Select from:
[1]. medicine;
[2]. agriculture;
[3]. science of force and motion;
[4]. science of heredity and variation;
[4].