【单选题】以下对TCP和UDP协议区别的描述,哪个是正确的()
A.
UDP用于帮助IP确保数据传输,而TCP无法实现
B.
UDP提供了一种传输不可靠的服务,主要用于可靠性高的局域网中,TCP的功能与之相反
C.
TCP提供了一种传输不可靠的服务,主要用于可靠性高的局域网中,UDP的功能与之相反
【单选题】Which of the following statements is true, according to the author of this passage?
A.
Certification is very common so you need to get certified, too.
B.
Certification is needed in a wide variety of fields, so may be in yours.
C.
Certification is varied because of more emerging careers and areas.
D.
Certification is becoming more and more important for every one.
【简答题】高炉煤气的化学成分中的可燃性成分主要有:CO、H2和微量的__________ ,所以高炉煤气是较好的气体燃料。
【简答题】高炉煤气和转炉煤气中的有毒成分是(),同时也是主要可燃成分。
【判断题】高炉煤气是低热值燃气,它的可燃发热成分主要是一氧化炭。