The bandwidth of a channel that carries digital data is usually measured in ___________.

With __________ , the user’s SSH client receives traffic with a given destination port number, places the traffic on the correct port and sends it to the destination the user chooses.

Fill in the blank(s) with the appropriate word(s).

Analyze the following code:

``` public class Test { public static void main(String[] args) { Object a1 = new A(); Object a2 = new Object(); System.out.println(a1); System.out.println(a2); } } class A { int x; @Override public String toString() { return "A's x is " + x; } }``` a. The program cannot be compiled, because System.out.println(a1) is wrong and it should be replaced by System.out.println(a1.toString()); b. When executing System.out.println(a1), the toString() method in the Object class is invoked. c. When executing System.out.println(a2), the toString() method in the Object class is invoked. d. When executing System.out.println(a1), the toString() method in the A class is invoked.