Cold weather clothing and equipment has evolved radically with the advent of synthetics. Traditional materials such as wools and eiderdown have given way to polypropylene and a myriad of other more plastic-like products. Though the old stand-by's still function as effectively as ever, they are no longer in favour with the more knowledgeable explorers, outdoorsman, and experienced general consumer. For all but those who are simply traipsing to and fro from the artificial heat of cars and buildings, there are many good reasons for the move to the synthetic materials, particularly when an individual is in a situation wherein he is relying on his own body heat to keep him warm.

Water retention in a material that is being worn or slept in is a critical factor in almost any cold weather environment. Moisture, be it in the form of precipitation, snowmelt, or perspiration, is the bane of the individual who elects to be outdoors. Vapour barrier garments aside, given the choice, one would wear clothing that retained no moisture whatsoever. It is in this area of extremely low water retention that synthetics excel. With synthetics, perspiration working its way to the surface of clothing becomes frost, which can be simply brushed away.

Surprisingly, the colder the weather, the less important this becomes. The most critical and dangerous temperatures are above thirty degrees and below fifty degrees for hypothermia. This is due to the melt-freeze cycles wherein one is constantly encountering rain, wet snow, and water. In extremely cold weather, it is also very dry. Sleeping bags and the like can actually be thrown out onto the snow in the sunshine to dry.

Wool, the traditional choice of the past, has hollow fibres and retains three percent of its weight in water when completely soaked and then hand wrung dry. Compared to cottons, this is phenomenal. However, modem polypropylenes, polar fleeces, etc. retain only one percent of their weight in water under the same circumstances. This is a remarkable difference. When this synthetic clothing is layered in the correct fashion, the individual's body heat actually causes moisture to move outwards to the surface of the clothing where it evaporates or can be wiped away. Additionally, the synthetics are not scratchy and irritating next to the skin like wool, as can be attested to by anyone who has worn a wool hat for any length of time and then switched to a softer, poly fleece-type hat.

According to the passage, which of the following are advantages of synthetics over more traditional materials in keeping people warm?

A. synthetics retain much less water than traditional materials and thus prevent the loss of body heat through evaporation
B. synthetics are breathable material and so prevent the generation of perspiration, which would lower the body temperature
C. synthetics can trap heat generated by the human body and thus keep a person warm even in sub-zero temperatures



Which of the following assertions is best supported by the information in the passage about the effectiveness of different materials in keeping a person warm?

A. Such materials will be most effective when the temperatures are above thirty degrees and below fifty degrees
B. There is an inverse relation between the effectiveness of such materials and the temperature of a place
C. There is a direct correlation between the effectiveness of such materials and their water retention capacity
D. Material considered the most effective a few decades ago may not be considered so any more
E. Wool is the most preferred choice of material for keeping people warm and has remained so in the past as well



From the information in the passage, in very cold weather, the importance of which of the following goes down?

A. The ability of a material to generate heat
B. The ability of a material to trap body heat
C. The water retention capacity of a material
D. The nature of fibres used in a material
E. The perspiration generation capacity of a material