首先告诉大家，我的论坛、博客、选课三大板块都开起来了（虽说选课还在完善，但这不重要），有时间可以去逛逛哈！（都在此网站主页）

Let's Beggggggggin!

★ First——invented machines

Event :Thousands of years ago，people invented machines.

Reason :It's hard to do it by manpower alone.

✰ Second——Levers

Event :People invented Levers.

Reason :Stop the beast in the night.

Result :At that time, people's work became easier and the lever became a kind of machinery.

Third——Rollers

Events :People began to move heavy objects with rollers.

Reason :People find it easier to move heavy objects with rollers.

Fourth——Ramps

Events :The Egyptians built pyramids with ramps.

Reason :None.

Result :Today, ramps are used in many places.

Fifth（Last）——Screws

Events :People(Who is he/she?)invented the screws.

Reason :We use it to fix(除了维修，还有固定的意思) sonething.

I think he is a genius!

Last(Real)

Today, we learned the development of machinery.Let's sort out its development:

OK, that's all the content of today's course.Thank you for all of you guys!