单选题 .  Every second,     21    hectare of the world's rainforest is destroyed. That equals to two football fields.
    This     22    rate of destruction has serious consequences     23    the environment. Scientists estimate, for example, that 137     24    of plant, insect or animal become     25    every day due to logging. In British Columbia,     26    , since 1990, thirteen rainforest valleys have been clear cut, 142 species of salmon have already become extinct, and the     27    of grizzly bears, wolves and many other creatures are threatened. Logging,     28    , provides jobs, profits, taxes for the government and cheap products of all kinds for consumers, so the government is     29    to restrict or control it. Much of Canada's forestry production     30    making pulp and paper. According to the Canadian Pulp and Paper Association, Canada     31    34% of the world's wood pulp and 49% of its newsprint paper. If these paper products could be produced in some other way, Canadian forests could be     32    . Recently, a possible     33    way of producing paper has been suggested by agriculturalists and environmentalists: a plant called hemp. Hemp has been cultivated by many cultures for thousands of years. It produces fibre which can be     34    paper, fuel, oils, textiles, food, and rope. For many centuries, it was essential to the economies of many countries     35    it was used to make the ropes and cables used on sailing ships; colonial expansion and the establishment of a world-wide trading     36    would not have been possible     37    hemp. Nowadays, ships' cables are usually made from wire or synthetic fibres, but scientists are now suggesting that the cultivation of hemp should be     38    for the production of paper and pulp. According to its proponents, four-times as     39    paper can be produced from land using hemp rather than trees, and many environmentalists believe that the     40    scale cultivation of hemp could reduce the pressure on Canada's forests.21.