Students are cleaning
Wanafunzi wanasafisha is not accepted, instead DL wants Wanafunzi wanafanya usafi. What is the difference, if any? [In School lesson].
Long answer to your short one:)
OK, that makes sense! However, there are many examples in this course where kusafisha is used without an object: hence the confusion by us learners.
Mama anapenda kusafisha. [does she, really?]
Kusafisha na kufagia