Explanation:

- Option 1, expanding: The universe is expanding. This conclusion comes from observations like the redshift of galaxies, which show they are moving away from us. This is supported by the Big Bang theory and discoveries like dark energy, which is thought to be accelerating this expansion.

- Option 2, contracting: There is no evidence that the universe is contracting. Current observations suggest expansion, not contraction.

- Option 3, remaining constant: A static universe is not supported by data. Earlier theories, like Einstein's cosmological constant, were replaced due to evidence for expansion.

- Option 4, splitting: There is no scientific basis for the universe splitting.