Denise sent in her solution.

1.There must be young ducks, but there don't have to be any old ducks. This is because if there were only old ducks, then they would all be greedy, and we know that there are some that aren't greedy.

2.This is true. We can't have a duck that is both not greedy and old, and there are ducks that are not greedy, so they must be young.

3. This is also true. If all of the young ducks were healthy, then they'd all be greedy. But all of the old ducks are also greedy, so then there wouldn't be any ducks that aren't greedy. So some of the young ducks are sick.

4. We don't know whether or not this is true. We could have old ducks that are sick.