You Go Hiking with Some Friends in a Nearby National

You go hiking with some friends in a nearby national park. The weather is cool when you set out but it quickly becomes very warm. Neither you nor your friends are carrying enough water. Eventually you find a stream and because you are so thirsty, you drink from it. About a week later you start to feel unwell. You have vomiting, abdominal cramps, and explosive diarrhea (loud, severe diarrhea) . Your stool seems kind of oily and is difficult to flush away. You tell your RN brother about your signs and symptoms, and he tells you he thinks you may have giardiasis, caused by the protozoan Giardia lamblia.
-Your brother tells you that most likely you ingested Giardia cysts that were in the stream water. He says you should have treated the water before you drank it. Which of the following would NOT have been a possible way for you to do this, as a hiker? 

A) Boiling the water.
B) Using a portable hiker's filter.
C) Using commercial water-purifying tablets (iodine) .
D) Using high pressure processing.
E) In fact, none of these would be possible for a hiker.