In spoken language, it sometimes happens that one person starts a sentence and another speaker finishes it, interrupting the first speaker. (This may be impolite in some situations, but not always).
A: I ...
B: ... clean the apartment today?
The verb clean doesn't change in first and second person singular.
In German, it would change:
B: mache / machst heute die Wohnung sauber?
Should B use mache to keep the predicate congruent with the subject or should B use machst to keep the meaning intact (i.e. A is the one who does something)?
I understand this is not really a question of grammaticality (since the subject changes mid-sentence), but of the usage of spoken language.