Here is the original item:
As he scrubbed the tile grout with a toothbrush and bleach. Nick vowed never
again to let the bathroom get so filthy.
You chose to connect the subordinate clause to the main clause that follows, like this:
As he scrubbed the tile grout with a toothbrush and
bleach Nick vowed never again to let the bathroom
get so filthy.
Unfortunately, you must do more than remove the period to connect these two parts correctly. Review the rules.