Why do you usually need more than one hypothesis for a question?

Q: a: in sexually reproducing animals, once fertilization of the egg takes place, the exists as a single cell until cell division begins

Which best describes the nucleus of an atom a. it is where all of the particle s of the atom are located b. it is the negatively charged part of the atom c. it is where the electrons and the protons are located d. it is the part of the atom with the greatest mass

9. the history of life on earth is recorded in