Final answer:
Sodium chloride (NaCl) will ionize in water because it is an ionic compound, separating into sodium (Na+) and chloride (Cl-) ions.
Step-by-step explanation:
The student's question is about which compounds will ionize in water. In this context, to ionize means that a compound dissociates into its constituent ions when dissolved in water. Among the given options, sodium chloride (NaCl) will ionize in water. This is because NaCl is an ionic compound, and when it dissolves in water, it separates into sodium (Na+) and chloride (Cl–) ions. Therefore, the correct answer to the student's question is that NaCl will ionize in water. Compounds like Fe(NO3)3 will also dissociate, but this was not given as an option in the student's provided choices.