单项选择题
Which network mask is the equivalent of 255.255.248.0?（）
A. /20 B. /21 C. /22 D. /23
多项选择题 Which two protocols use UDP as a transport protocol by default?（）
多项选择题 Which three protocols use UDP as a transport protocol by default?（）
多项选择题 You have been asked to develop an application that uses only connection-oriented protocols. Which two protocols can you use?（）
