Exercise B

Could there be:

1. A valid argument that has one false premise and one true premise?

2. A valid argument that has only false premises?

3. A valid argument with only false premises and a false conclusion?

4. An invalid argument that can be made valid by the addition of a new premise?

5. A valid argument that can be made invalid by the addition of a new premise?

In each case: if so, give an example; if not, explain why not.