任何非空树中有且仅有一个结点没有前驱结点，该结点就是树的 【2】 。

女士，39岁，曾于3年前发现患有子宫浆膜下肌瘤，肌瘤直径为2.8cm，月经规律，经量较多，应采取何种避孕方法（）。

A.工具避孕

B.口服药避孕

C.输卵管结扎（绝育）

D.放置宫内节育器

E.皮下埋植避孕法

等级相关分析是（）。

A.参数统计分析法

B.非参数统计分析法

C.正态资料统计分析法

D.偏态资料统计分析法

E.等级资料统计分析法

阅读理解

A young, dark haired woman appeared in the doorway.

"Good morning, children! My name is Mrs. Murray. I am replacing your regular teacher," she said, as

she wrote her name on the blackboard. "I will enjoy getting to know each of you personally, over the

next few months."

The children in the class remained silent, as this was totally unexpected.

"Come on, someone say something," she thought nervously. The children were too quiet.

"This probably won't last long," she thought, smiling kindly at them. Grade Three students were normally

very lively and seldom, if ever silent. "If you have problems, please come to me. I will help you."

The children gradually began to relax, but not one of them spoke.

"How can I get them to accept me?" she wondered. Suddenly, she had an idea.

"Your first homework will be to write a new song. To make it even more exciting, challenging and fun for

everyone, it must be a new love song for Valentine's Day. The winner will be awarded a prize, at our class party."

The children looked amazed, but pleased.

"You may sing your new song, or play it with a musical instrument."

As if something had suddenly awakened the children, the silence in the room ended suddenly.

"A love song?" a boy asked, smiling sweetly, at his new teacher.  

"We each have to write one," said a dark haired girl, "We never had to do that before."

"And perform it too!" a red haired boy responded, laughing aloud. "I love it! Me, sing a love song?"  

"Want to know what the first prize will be?"

Immediately, every hand in the room went up.

Mrs. Murray reached into her handbag and pulled out a harmonica(口琴).

"What do you think of this?" She waited.

"I am also a music teacher, so I will be able to help you write your new love songs." added Mrs. Murray,

smiling at her new students. Obviously, her smile and intelligent idea about the homework impressed every student in the class.

1. The children remained silent at the beginning because __________.

A. they missed their former teacher

B. they were surprised at the situation

C. they didn't know the teacher's name

D. they were not allowed to speak in class

2. We can learn from the passage that __________.

A. children in the class liked to write their own love songs

B. most children in the class were good at performing music

C. it was the prize that made the students accept their new teacher

D. the students in this class are not as active as other Grade Three students

3. Which of the following words can best describe Mrs. Murray?

A. Kind and curious.

B. Helpful and clever.

C. Faithful and honest.

D. Patient and humorous.  

肾小管重吸收受损可检出的标志物不包括( )

A．α₂-微球蛋白
B．α₂-巨球蛋白
C．β₂-微球蛋白
D．溶菌酶
E．尿蛋白

工程量清单计价模式下，投标人编制施工图预算时采用的工、料、机消耗量反映( )。

A．社会平均水平

B．行业平均水平

C．地区平均水平

D．投标人自身水平