The answer is D. Creek water can contain bacteria called giardia and cryptosporidium. These can make you very ill, and they can't be filtered out by tight lips or clothing; nor are they eliminated by the aeration of roily water. Only boiling, chemical action or low-micron-level filtration will make the water safe to drink. The best you can do in this situation is to conserve your body fluids by resting in the shade until the day cools. Then hike slowly to avoid dehydration. Even though you really want a drink, you are probably not in a serious dehydration survival situation if you've spent no more than one hot morning fishing on the stream. Next time, carry a personal water supply, and take along a water-purification filter as part of your survival kit.