To put it in its simplest terms:
- dissociation: when a compound breaks down into its individual components: for example the molecule N2(g) can dissociate into two nitrogen atoms, also HCl(g) can dissociate into its component gases.
- ionisation: this infers a change in solution (usually aqueous solutions), where by acids will ionise into the component ions.
using that distinction, try to figure out which examples correspond two which process.
goodluck,
george