Their children ________ in the park for over an hour when it suddenly rained.Đoạn văn1/29I. PHẦN TRẮC NGHIỆM VÀ CÂU TRẢ LỜI NGẮN GRAMMAR Mark the letter A, B, C, or D on your answer sheet to indicate the best answer to each of the following questions. Their children ________ in the park for over an hour when it suddenly rained. have played had been playing are playing playedGiải thíchB. had been playing