_____,he can be fluent in English.[ ] A.

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问题选择题

_____,he can be fluent in English. [ ]

A. Child as he is

B. As he is a child

C. As child he is

D. Strange as is he

答案

单项选择题

图Ⅱ—9所示的轮系中，z₁=20，z₂=40，z_2’=15，z₃=45，z_3’=20，z₄=40，z_4’=2，z₅=80，z_5’=10，m_5’=2mm，n₁=600r/min，则齿条6的移动速度和方向为______。

问答题简答题

品种内杂交和品种间杂交有什么区别？