Holonyak's colleagues thought he would fail in his research on LEDs at the time when he started it.

• A、True
  
  

• B、False
  
  

• C、Not Given
  
  

假设你的美国朋友Mike要去你的家乡旅游，请给他写一封电子邮件，告诉他:

1. 近期的天气情况；

2. 需要注意的事项；

3. 你期待与他见面。

请以 Like 署名

According to the passage, which aspect of skyscrapers were some residents of North America concerned with in the late 1960's?

• A、The poor reception of radio and TV signals.
  
  

• B、The removal of trees and grass from building sites.
  
  

• C、The harmful effects on the city's plans.
  
  

• D、The obstruction of air traffic