覆盖优化可以通过调整天线的方位角、增加天线挂高等方法实现。()
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空气净化技术中，以()粒径的粒子作为划分洁净等级的标准粒子
A. 0．5μmn
B. 0．5μm和5μm
C. 0．5μm和0．3μm
D. 0．3μm和0．22μm
E. 0．22μm
能保持稳定的净化气流使微粒不沉降、不蓄积的方法称为()
A. 灭菌法
B. 空调法
C. 层流净化技术
D. 旋风分离技术
E. 高效滤过技术
According the interviewee, which is an obstacle of the research？
A. People with different backgrounds have different understanding of healthy food.
B. Supermarkets are afraid that healthy food may bring them less profit.
C. It is hard to trace people"s food choice in small community stores.
D. People find it harder to preserve the healthier food at home.
According to the interview, which of the following food is considered as healthier food？
A. Soda water.
B. Chips.
C. Fresh Spinach.
D. Ice-cream.
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