economics normal profit This sharp reversal contrasts with the flattening of the previous yield curve. From the end of the 19th century to the early 20th century, car designers focused their energies on the development and innovation of mechanical engineering. First half of the 20th century, all about the basic structure of the car has been invented, automotive designers begin from the outside to improve on modelling, and successively introduced the aerodynamics, fluid mechanics, human body engineering and industrial modelling design (industrial aesthetics), etc The form of shares is the share certificate. Different types of joint-stock enterprises, the specific form of their share certificates are different. Among them, only the limited company is used to express the company shares the form is the stock. Stock shall be recorded according to the amount of capital represented by the shares and shall be recorded by shareholders' share of capital contribution and shareholder rights for the public subscription and transfer of transactions. Holding a stock means owning a stake in a limited company, acquiring a shareholder's qualification, and exercising shareholder rights. Is one of the more common usage refers to various enterprises independent, non-profit organization (can be legal person, also can not), and can be further divided into companies and enterprises, the latter such as partnerships, sole proprietorship enterprise, individual industrial and commercial households, etc.