问题 单项选择题

对如下二叉树,进行后序遍历的结果为【 】。

A.ABCDEF

B.DBEAFC

C.ABDECF

D.DEBFCA

答案

参考答案:D

解析:后序遍历可以描述为:若二叉树为 空,则空操作;否则:①后序遍历左子树;②后序遍历右 子树;③访问根结点。对于后序遍历,第一个访问的结点一定是最左下的结点,最后一个访问的结点一定是根结点,如果知道这个小技巧,可以迅速确定本题的答案为选项D)。

填空题

动词填空。阅读下面短文,用括号内所给动词的适当形式填空(必要时可加情态动词或助动词)。

     "Everything happens for the best," my grandmother said whenever things weren't going my way.

"Don't worry, one day your luck (1) _______ (change)."

     Grandmother was right, as I discovered after graduating from college. I had decided to be sports

announcer (广播员) in a radio station, so I (2) _______ (go) to Shanghai and knocked on the door

of every station. But I got refused every time.

     In one station, a kind lady said my problem was short of experience." Get some work with a small

station and (3)_______ (work) your way up," she said.

     I couldn't get a job there, either. Then my dad told me a businessman had opened a company and

needed someone (4)_______ (manage) the sports center. But again, I didn't get the job.

     I felt really down. "Your luck will change," Granny reminded me. I tried another radio station in

Beijing. But the owner, a nice man, told me he already had someone.

     As I left his office, I asked," How can someone be a sports announcer if he (5)_______ (not, get)

a job in a radio station?"

     I (6)_______ (wait) for the elevator when I heard the man call, "What was that you said about sports?

Do you know anything about football?" I (7)_______ (put) in front of a microphone and asked to imagine

I was commenting (评论) on a football game. "Now you (8)_______ (watch) the football game between

Lu Neng and Shen Hua..."

     On my way home, Granny's words came back to me, "One day your luck will change, boy. And when

it (9) _______ (happen), it'll feel twice as good because of all the disappointment (失望) you (10) _______

(have)." At that moment I knew just what she meant.

选择题