Someone who is irresolute is unable to decide what to do.
Dissolution is the breaking up or official end of a group, such as a couple or institution; it can also be the act of separating something into smaller components.
If you know something with absolute certainty, you are total or complete in your belief in it.
A solution to something, such as a problem of some kind, is a way to figure it out or deal with it so that an answer is found.
Differentiated vocabulary for your students is just a click away.