【正确答案】：49. It means to make great efforts.
50. It refers to the advancement if technology.
51. It means that's those things mentioned above that have made Korea a rising world trade power and able to compete with countries like the U.S and Japan in the internationl market.
【题目解析】：49. sweat意为”努力“。50. technological sophistication指的是尖端技术，先进技术。51.  意味着，正是上述的因素使韩国成为一个正在崛起的世界贸易大国，并有能力与美国等国展开竞争。我们的产品在国际市场上畅销不衰。