The residue from the experiment after the evaporation was salt. It took a long time to clean up the residue of flour from the kitchen floor.
The adhesive tape left a sticky residue on the glass.
When it has a subject, verb, punctuation, capitalization, a predicate, and a complete thought. A sentence is a sentence when it is handed down by a judge (or a magistrate).
"Our community worked on keeping our ecosystem clean."
This is one of a series of questions copied from Penn-Foster's "Practical English" quiz.There is no answer here.