搜题请搜索小程序“爱下问搜题”
问题 选择题

下列物质中一定有两种元素的是（　　）

A．氧化物

B．化合物

C．混合物

D．单质

答案

氧化物一定含有两种元素．化合物可能是两种，也可能是多种．混合物组成不固定，可以有多种或一种．单质中只有一种元素．

故选A

单项选择题

In the dining room of my grandfather’s house stood his heavy dock. Meals in the dining room were a (16) for our four generations to become one. My grandfather’s clock always stood like a trusted old family friend, (17) us playing jokes and telling stories, which was already a (18) of our life.
When I was a child, the old clock interested me. I watched and listened to it during (19) I was surprised how at (20) times of the day, the clock would strike three times, six times or more, with a wonderful great (21) that echoed throughout the house. The clock chimed year after year, a part of my (22) , a part of my heart.
Even more (23) to me was my grandfather’s special action each day. He meticulously (24) the clock with a special key each day. The key was magic to me. It (25) our family’s magnificent clock ticking and striking all year round.

Ⅱ．完型填空/Cloze

A．busy

B．urgent

C．happy

D．different
查看答案
问答题 简答题

简述复凝聚法制备微囊的基本原理。
查看答案