An administrator is unable to ping any address on the 10.0.19.0/24 subnet. To identify the problem, the administrator uses the command shown in the exhibit.
Which step should be taken to solve the problem?（）

单项选择题You have been asked to use a 23-bit network mask to segment the network block 209.18.12.0. How many usable host addresses will there be per subnet?（）

A. 510
B. 1022
C. 2046
D. 8190

单项选择题You have been allocated a 22 network. How many usable hosts are available?（）

A. 510
B. 512
C. 1022
D. 1024

单项选择题What are the usable hosts on the .128.0 19 network?（）

A. .128.1 through .143.254
B. .128.128 through .134.254
C. .128.0 through .134.254
D. .128.1 through .159.254

单项选择题You must segment your internal 24 network into a minimum of 12 subnets, each containing a minimum of 12 hosts. Which network mask do you use?（）

A. /26
B. /27
C. /28
D. /29

单项选择题You have been assigned the 24 network and need to segment it into at least 60 subnets. Which network mask meets this requirement?（）

A. /27
B. /28
C. /29
D. /30