thatCleft sentence: "It was in the 19th century _____ the foundations of modern public health were laid."It was in the 19th century that the foundations of modern public health were laid.NoteIt was in the 19th century that the foundations of modern public health were laid.Elon.io is an online learning platformWe have an entire course teaching IELTS Vocabulary — Band 7+ grammar and vocabulary.Start learning IELTS Vocabulary — Band 7+ now