Need help with one step dimensional analysis

Fill in the coefficients that will balance the following reaction: a0cr2(so4)3 + a1agno3

When balancing a chemical equation:

What happens when an atom of sulfur combines with two atoms of chlorine to produce sci2? a. each chlorine atom shares a pair of electrons with the sulfur atom. b. an electron is transferred from each chlorine atom to the sulfur atom. c. an electron is transferred from the sulfur atom to each chlorine atom. d. each chlorine atom shares all its valence electrons with the sulfur atom.