(Java) Object oriented

1. Consider the following code:

Object o = "abc";

For each of the following statements, indicate whether or not a compile-time error will occur, and for those statements that are legal at compile time, indicate whether they will return normally or by throwing an exception; if the return is normal, also indicate the result.

boolean b = o.equals("a, b, c");

char c = o.charAt(1);

Object o2 = b;

String s = o;

String t = (String) o;

c = t.chatAt(1);

c = t.charAt(3);