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.

请根据对话选词填空

   ducks    quiet     nature park    people   buildings

    There is a____. The nature park is____. There aren't many ____. There aren't many tall____. There are some animals. They are____and rabbits.

化简：$\sqrt{\frac{x^{2}y}{x}}$•$\sqrt{xy}$=（　　）