题干

已知结论:“在正三角形ABC中,若D是边BC的中点,G是三角形ABC的重心,则
A
G
G
D
=2
。若把该结论推广到空间,则有结论:“在棱长都相等的四面体ABCD中,若BCD的中心为M,四面体内部一点O到四面体各面的距离都相等”,则
A
O
O
M
=
(   )

A:1

B:2

C:3

D:4

上一题 下一题 0.0难度 选择题 更新时间:2014-03-20 03:51:14

答案(点此获取答案解析)

C

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阅读理解

    If you have ever been left wondering why your emails are riddled(充斥着) with grammatical errors, or why you can never quite find the right phrase, it may be because you are typing with both hands.

    Our vocabulary becomes richer and our writing style becomes more fluent when we type using just one hand, scientists have found. "Typing can be too fluent or too fast, and it can actually weaken the writing process," said Srdan Medimorec, the lead author of the study conducted at the department of psychology at the University of Waterloo, Canada. "It seems that what we write is a product of the interaction(互动) between our thoughts and the tools we use to express them."

    Using text-analysis software, researchers asked 103 university students to write essays under different conditions, using one hand to type and using both hands to type. The software was used to analyze(分析) elements of the essays, such as range of vocabulary, sentence complexity and the cohesion(衔接) of the writing.

    Researchers found that participants' vocabulary became more advanced when they typed with one hand rather than two. The research team said that by slowing our writing down, typing one-handed allows more time for an internal (内在的) word search, resulting in a larger variety of words.

    In contrast, fast typists might just write the first word that comes to mind. However, it is important not to slow typing down too much. Those who typed essays one-handed in the current study slowed down to about the speed of handwriting.

    This is the first study to show that changing people's typing can make their writing get better. The researchers suggested that the speed of writing could affect writing quality regardless of the tools used, whether they are computers, or pen and paper, although further research would be required to prove that idea.