这条航线连接了亚洲和北美的主要城市。

This ___airway connects major cities between Asia and North America.

哮喘发作时，患者的气道会变得狭窄。

During an asthma attack, the ___airways become narrowed.

这家航空公司提供飞往全球200多个目的地的服务。

The ___airways offer services to over 200 destinations worldwide.