单项选择题
A. application
B. presentation
C. session
D. transport
E. internet
F. data link
单项选择题 Refer to the exhibit, Host A pings interface S0/0 on router 3, what is the TTL value for that ping?（）
单项选择题 Which layer in the OSI reference model is responsible for determining the availability of the receiving program and checking to see if enough resources exist for that communication?（）
多项选择题 Refer to the exhibit. Which three statements correctly describe Network Device A（）