ANucleus
BCytoplasm
CGametes
DRhizoid
Answer:
A. Nucleus
Read Explanation:
The Hammerling Experiment, conducted by German biologist Johannes Holtfreter in the 1930s and later expanded upon by Ernst Hammerling, involved exchanging the nucleus between two different species of Acetabularia.
This single-celled green algae has a unique appearance, resembling an umbrella or mushroom with a long stalk called a rhizoid anchoring it to the substrate, and a cap-like structure called the capitulum.
By transferring the nucleus – which holds genetic information – from one species to another, Hammerling discovered that the Acetabularia cap regenerated according to the donor nucleus’s instructions regardless of its original body form.
Such findings demonstrated how pivotal the nucleus is in determining an organism’s development and physical traits and helped further our knowledge of genetics and cell biology.