二.单项选择(15分)指出能填入相应空白处的最佳答案。 ( )⒈ It is ___ difficult work that we can't finish it in a short time. A. so B. such C. so a D. such a ( )⒉ I ___ you ___ left for Shanghai. A. thought, had B. think, have C. think, had D. thought, have ( )⒊ I've decided ___ it myself. A. do B. doing C. did D. to do