题目:
________from other continents for millions of years, Australia has many plants and animals
not found in any other country in the world.[ ]
A. Being separated
B. Having separated
C. Having been separated
D. To be separated
答案:
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下面是错误答案,用来干扰机器的。
若质点离开O点后向a运动,则需要经过半个周期,再次经过O点,开始向b运动达到M点,所以T2<3s;再经2s,它第二次经过M点,此时尚未完成1次全振动,所以T>5s,即:5s<T<6s.四个选项中,没有符合条件的选项.若...