。
She took care of the children.
Literal
She [topic-は] children [genitive-の] care [object-を] did.
A textbook example of the ~の世話をする pattern: the noun phrase 子供たちの世話 ('care for the children') becomes the object of する with を. Among the most useful set expressions in Japanese for caregiving and looking after — applies to children, pets, plants, the elderly, even guests. The related phrase ~の世話になる ('to be in someone's care, to be indebted') is the polite reciprocal: a guest leaving will often say お世話になりました ('thank you for taking care of me').