【判断题】趋势分析和散点分析都假定生产率在各年都保持不变。
【单选题】He commanded that the student _____the classroom before he returned.
【单选题】He ______ the key, so we ______ into the office.
B.
didn’t leave; couldn’t have got
C.
hadn’t left; couldn’t get
D.
hasn’t left; couldn’t get
【单选题】We didn’t look after the old woman ____ we had an important meeting yesterday. [ ]