Given the classes Student and CollegeStudent, as described in the previous exercise, which of the following statements are legal and which you think are not? a. Student bob = new Student(); b. Student...

Given the classes Student and CollegeStudent, as described in the previous exercise, which of the following statements are legal and which you think are not?

a. Student bob = new Student();

b. Student bob = new CollegeStudent();

c. CollegeStudent bob = new Student();

d. CollegeStudent bob = new CollegeStudent();