Please Answer all of the following. THanks!

What is a sinking fund?

What are the two most common protective covenants in most corporate bonds?

Are most corporate bonds callable or not callable?

Is the call option good for the corporation or good for the investor?

When do corporations call their bonds when interest rates go up or when interest rates go down?

Who are the two largest credit rating agencies for corporate bonds?

What risk is the rating agencies rating when they rate bonds?

Securities that are rating with the top four credit ratings are considered what?

What are the inferior rated (less than the top four ratings) bonds called?

Are most bonds traded like stock or bought and sold (or held to maturity) through investment bankers?