【简答题】我们日常生活中的可见光的波长范围为()nm。光纤通信所用的光波长范围在()nm的近红外区。
【简答题】Use the useful expressions in the text to finish the sentences: Several years ago my daughter Mimi and I ______ _______ _____(尝试)running the NewYork Marathon.
【判断题】接触器除通断电路外,还具有短路和过载保护功能
【判断题】抑制法灭火原理是:灭火剂渗入到燃烧反应中去,夺取助燃游离基。( )
【简答题】Write a letter of complaint of about 120 words to describe the picture below. Some useful expressions are provided to help you. You may start the passage with the sentence “On July 16 my friends and I...
【判断题】接触器除通断电路外,还具有短路和过载保护功能
【单选题】抑制法的灭火原理是()。
A.
将灭火剂直接喷洒到燃烧物上,使可燃物的温度降低到燃点以下
D.
化学灭火剂喷入燃烧区参与燃烧反应,终止燃烧链反应