日军打通“大陆交通线”战役的直接目的是 [ ]
A、迫使国民党政府投降
B、扩大对华南的经济掠夺
C、强化对占领区的统治
D、援救侵入南洋的日军
答案：D
He practiced as often as he could _____ his spoken English. [ ]
A. improve
B. improving
C. to improve
D. improved
曲线x2+y2=2x在点(1，1)处的切线方程为______．
