Organisms in the same ecosystem are all

The question is asking us to say what organisms in the same ecosystem are.

Organisms in one ecosystem are all dependent on each other: they feed on each other or are dependent on the tissues of the other organisms when they die - this is called "interdependence" - dependence from each other.

So the answer is interdependent.

Organisms in the same ecosystem are all co-existing.

There is no reason to think the results are biased or not conducted properly but you should not assume the results are correct just because they were done in a laboratory so the answer would be c. it is likely to be reliable because the results support the conclusion presented.