Which is not key requirement/premise for an efficient securities market?

(A) Prices must be efficient so that new inventions and better products will cause a firms' securities prices to rise and motivate investors to buy the stocks

(B) Information must be discussed freely and quickly across the nations so that all investors can react to the new information

(C) Transaction costs such as brokerage on sale and purchase of securities are not ignored

(D) Investors are rational and make investments in the securities providing maximum yield