Adverb clauses

I learned that an adverb clause needs to meet three requirements.

• It will contain a subject and a verb
• A subordinate conjunction (next weeks post ha ha) keeps the clause from expressing a complete thought
• And the clause answers one of these three adverb questions: How? When? or Why?
  

e.g. Tommy scrubbed the bathroom tile until his arms ached.
The how question is answered. until his arm ached.

http://www.chompchomp.com/terms/adverbclause.htm