4.there are too many rabbits in somewhere australia---too bad for its ecological system. so some govenment agent advocates to kill rabbits by putting poison on grass rabbits feed on. but some others say that this will also poison billy, an endangered species. Weaken my key: too many rabbits will eat up most of foods billy depends on.
5. City officer: five year ago we changed something in hospital A. today we see the positive result--less cost per paitient in A than in other hospital unchanged. so we should apply same changes to the others. Assumption: hospital A does not move those patients in severe condition(more cost) to the others.