循环水系统中加入的化学药剂主要是（）、（）。

     I have two friends who are eager for travel, There is a part of New York's Adirondack Mountains that is
called the High Peaks. It consists of 46 mountains with the height of over 4 000 feet.
     The Adirondack Mountain Club gives a small piece of land to anyone who   1   all the 46 mountains. My
two friends decided to go for this   2  . It took them several years to accomplish it; it was hard to achieve.
Many of the 46 mountains have   3   and well-used walkways to their tops. However, others are not marked
at all. These mountains are really hard to climb   4   travelers have to bushwhack (在丛林中开道) them using
 a compass and a map.
     My   5   had climbed 45 of the mountains. They had one left that was the highest, requiring bushwhacking.
They left their camp site early one   6   and walked to the foot of the mountains. When they reached the foot
they found that they had   7   their compass and the map in the camp. Rather than returning to the camp, they
decided to bushwhack without the compass and map. For nearly ten hours they walked uphill   8   heat, thick
bushes and black flies. Finally, late in the afternoon they found themselves at the top of a mountain. They were
exhausted but excited. But the excitement   9   disappeared. They saw another higher mountain when they
looked across the valley. They had climbed the  10  hill! It was too late that weekend to correct their mistake.
They had to  11  4 months to climb the right mountain because it was also the remotest one.
     Often in life we use great effort toward some  12 . But without the right map and personal compass, it is
easy to get lost. Knowing your life purpose gives you a powerful personal map and compass that makes sure
you are always climbing the right mountain.