关于口腔正常菌群，说法错误的一项是A．刺激宿主免疫系统B．营养

搜题请搜索小程序“爱下问搜题”

问题单项选择题

关于口腔正常菌群，说法错误的一项是

A．刺激宿主免疫系统
B．营养功能
C．作为生物屏障，抑制外源微生物
D．一般对宿主无益，甚至有害
E．维持口腔或全身微生物的生态平衡

答案

参考答案：D

句型转换

1. Donna began to learn the accordion at the age of nine.(与the violin构成选择疑问句)

_____ Donna _____ to learn the accordion _____ _____ _____ at the age of nine?

2. I took part in the sports meeting last week.(改为否定句)

I _____ _____ part in the sports meeting last week.

3. He didn't catch the early bus because he got up late.(对画线部分提问)

_____ _____ he catch the early bus?

4. He was a small boy. He began to learn music.(用when合并句子)

He _____ _____ learn music _____ he was a small boy.

5. My father played for Liverpool football team.(改为同义句)

My father _____ a _____ _____ Liverpool football team.

选择题

“停车坐爱枫林晚，霜叶红于二月花”，从细胞知识来看，引起枫叶颜色变化的物质存在于

A．叶绿体

B．细胞核

C．液泡

D．细胞壁