During the lecture, Rosie was busy ________ so she could review the key points later.
Giải thích
making notes
Tobe busy + V-ing: bận làm gì
=> During the lecture, Rosie was busy making notes so she could review the key points later.
(Trong suốt bài giảng, Rosie đã bận ghi chép để có thể xem lại các điểm chính sau đó.)