Determine if the event described is independent or dependent.
you pick a marble at random from a group of marbles, don't replace the marble, and pick a second marble

They are dependent events, because the probability of the second event depends on the result of the first event

If you replace the marble before picking up the second marble, then the first event didn't affect the second result ant the events were independent.

Given that you did not replace the marble, the second pick up has different probailities depending on the first result.