A polynomial is a function where the only operation is an exponent on the variable. It can have just one term or many terms. For example, x^2 is a polynomial but x^2 / x+3 is not since it also contains division. This is a rational. Using this definition then only C and E are polynomials.
Choice A has a rational term. This is not polynomial.
Choice B has an exponent of -2 which is actually division. This is rational and not polynomial.
Choice D has a radical term with the variable. This is not polynomial.
The events are independent. By definition, it means that knowledge about one event does not help you predict the second, and this is the case: even if you knew that you rolled an even number on the first cube, would you be more or less confident about rolling a six on the second? No.
An example in which two events about rolling cubes are dependent could be something like:
Event A: You roll the first cube
Event B: The second cube returns a higher number than the first one.
In this case, knowledge on event A does change you view on event B (and vice versa): if you know that you rolled a 6 on the first cube you don't want to bet on event B, while if you know that you rolled a 1 on the first cube, you're certain that event B will happen.
Conversely, if you know that event B has happened, you are more likely to think that the first cube rolled a small number, and vice versa.
