据英国广播公司报道，德国汉堡大学的天文学家在银河系中发现了一颗已有140亿年历史的恒星，它的形成能够追溯开宇宙形成的初期。这颗恒星被编号为HE0107—5240，其罕见之处在于：与其他历史稍短的恒星不同，它完全是由宇宙大爆炸时产生的几种简单元素组成的，是迄今为止发现的第一颗不含金属元素的恒星。

我国最后完成经济重心南移是在（    ）

B:He ____ to to Beijing  ____  ____.

    A patent is an official document____(give)to an inventor by a government. This document ____(general) gives inventors the right to stop anyone else from copying, using or selling the invention without their permission.

    Inventions are the result of hard work. It may only take a moment of inspiration to think of a good idea but it takes a lot of research and experimentation to turn it into a(n)____ (use)and working invention. So, inventors deserve a reward for the amount of time they spend ____(develop)their ideas. They also need the ____(secure) of knowing that if they share the invention with ____rest of the world, nobody will steal it, use it or copy it without their permission.

    Patents also benefit the society ____return for patent protection. Inventors agree____(show)all the technical information about their invention. This information is available to everyone and has enough details ____can be used by people with basic knowledge to produce the invention. In this way, patents help to spread new knowledge, which can in turn help people find ____(solve)to different problems or to make further advances in science and technology.