Which of the following is the most plausible first step in the solvolysis [sawl-VAWL-eh-sis] of tert-butyl [turt-BYU-til] iodide in water?

W) Concerted substitution

X) Attack of water to form a pentavalent [penta-VAY-lent] intermediate

Y) Decomposition to form positively-charged intermediate

Z) Decomposition to form negatively-charged intermediate
Y) DECOMPOSITION TO FORM POSITIVELY-CHARGED INTERMEDIATE