Question

which principle is part of cell theory?
all organisms are multicellular.
all cells have a nucleus.
cells come from pre - existing cells.
cells form spontaneously.

Explanation:

Cell Theory states that all living things are made of cells, cells are the basic units of life, and cells come from pre - existing cells. Unicellular organisms exist (so "All organisms are multicellular" is wrong). Prokaryotic cells (like bacteria) do not have a nucleus (so "All cells have a nucleus" is wrong). The idea of spontaneous generation of cells has been disproven (so "Cells form spontaneously" is wrong).

Answer:

Cells come from pre - existing cells.