题目

Unfortunately, when I dropped in, Doctor Li _____ for Beijing to join in the fight again SARS, so we only had time for a few words.   A. just left                     B. has just left      C. is just leaving               D. was just leaving   答案：D动词时态的考查。当我去看他时，他正要去北京参加抗击非典，所以只跟他说了几句话。情景是他正要去。又因为come，leave，arrive等动词的进行时表将来时，故答案为D.  下列各组离子在无色溶液屮可以大最共存的是（　　） A、NH4+、NO3-、OH-B、Ca2+、OH-、HCO3-C、Na+、S2-、Cl-D、Fe3+、Na+、Cl-