đừng đáp án không nhé, tìm chỗ để khoanh á In the early 1800’s, the paper industry was still using rags as the basic source of fiber as it had for many centuries. However, the rag supply couldn’t keep up with the growing demand for paper. The United States alone was using 250,000 tons of rags every year. And a quarter of that had to be imported. It was clear that the new source of fiber was needed to keep up with the demand for paper. The answer to this problem turned out to be paper made from wood pulp, something that was abundantly available in North America. In Canada, the first wood pulp mill was set up in 1866 and was immediately successful. But while wood pulp solved the problem of quantity, it created the problem of quality. Wood contains a substance called lignin. The simplest way to make large quantity of cheap paper involves leaving the lignin in the wood pulp. But lignin has poor structure and its presence in paper has shortened the life expectancy of paper from several centuries for rag paper to less than a century for paper made from wood pulp. This means that books printed less than a hundred years ago are already turning yellow and beginning to disintergrate, but rag paper books printed much earlier may be in fine condition. This is bad enough for the older books on your bookshelf, but it poses a huge problm for libraries and collection of the government documents. 36. In the early 1800’s, the rag supply was scare because_________. A. rag was the basic source of industry B. the demand for paper was growing C. wood pulp had its shortcoming D. the rags had to be exported 37. The resolution of scarce rag supply was_________. A. to find new source of fiber B. to import a quarter of rags used in the United States C. to use wood pulp, which was abundant in North America D. to build more mills in Canada 38. Paper made from wood pulp_________. A. was better than rag paper. B. had short life expectancy C. would begin to turn yellow soon D. would begin to disintegrate soon 39. The poor quality of paper was caused by_________. A. presence of lignin in wood pulp B. wood pulp C. lack of lignin in wood pulp D. being kept for centuries 40. Books printed in paper made from wood pulp would cause a problem that is_________. A. equally serious for both older-book owners and libraries B. worse for libraries than government documents C. worse for older-book owners than for libraries D. worse for libraries than for older-book onwers