单项选择题 How would the number 231 be expressed as a binary number?（）

单项选择题 Which one of the binary number ranges shown below corresponds to the value of the first octet in Class B address range?（）

单项选择题 The subnet mask on the serial interface of a router is expressed in binary as 11111000 for the last octet. How do you express the binary number 11111000 in decimal?（）