放大器在工作时,造成工作点不稳定的各种因素中()是主要因素
A、温度变化
B、电源波动
C、晶体管老化
D、负载变化
参考答案:B
阅读判断所给句子的正确“T”或者错误“F ”。
I am an American boy. My name is Jerry Black. You can call me Jerry. I have a sister, Ginny. We are
twins (双胞胎). But we are very different. I have a long face with a high nose, while she has a round face
with a small nose. I like meat and rice. But she likes vegetables and wheat. I like loud music. She likes light
music. My father is a doctor in a hospital. My mother runs (经营) a clothing store. We have another family
member, Beibei. She is a cute dog. She will have a puppy (小狗) soon.
( )1. Jerry and Ginny are twins.
( )2. Ginny's father is Mr. Black.
( )3. Jerry and Ginny look the same.
( )4. Jerry's mother has no job.
( )5. Jerry's family has five members.
每个城市对周围地区都有一定的吸引力,其吸引力的大小与下列哪个因素的关系最密切( )
A.城市性质
B.城市功能
C.城市的产业结构
D.距城市的远近