问题
选择题
Sarah made ___ to the airport just in time to catch her plane this morning. [ ]
A. herself
B. this
C. that
D. it
答案
答案：D
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Sarah made ___ to the airport just in time to catch her plane this morning. [ ]
A. herself
B. this
C. that
D. it
答案：D
R，A环仍从离底部2R处静止释放，则A环经过半圆形底部再次上升后离开底部的最大高度为多少？ 