问题
单项选择题
树是结点的集合，它的根结点的数目是( )。
A．有且只有1个
B．1或多于1
C．0或1
D．至少有2个
答案
参考答案：C
解析： 树具有明显的层次关系，即树是一种层次结构。在树结构中，根结点在第一层上。当树为非空时，树中有且只有一个根结点；当树为空时，树中根结点的数目为0。
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树是结点的集合，它的根结点的数目是( )。
A．有且只有1个
B．1或多于1
C．0或1
D．至少有2个
参考答案：C
解析： 树具有明显的层次关系，即树是一种层次结构。在树结构中，根结点在第一层上。当树为非空时，树中有且只有一个根结点；当树为空时，树中根结点的数目为0。
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| Two brothers worked together on a farm. One was married and had a large 1 . The other had no wife yet. Although they lived in different houses, they shared everything they got from their farm. One day, the single brother said to himself, "It's not 2 that we share all the rice. I'm 3 and I need less than my brother." So, every night he took a bag of rice from his store-room and 4 across the field 5 their houses, putting it into his brother's store-room. At the same time, the married brother thought, "It's not fair to share all the rice. I'm married and I have my wife and children to 6 me when I am 7 . However, my brother has no one to take care of his 8 " So, each night he also took a bag of rice and put it into his brother's store-room. Several months passed by. They found 9 strange that their rice never became less. Then, one dark night the two brothers ran into each other. Slowly they began to understand what was happening. Their bags fell onto the ground and tears 10 their eyes at once. | ||||
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