Do "margin" in the stock market and "margin" in the futures market, respectively, mean that an investor has received a loan that reduces the amount of his own money required to complete the transaction（）

单项选择题An analyst does research about moneyness of stock options. With respect to stock options, the potential for an infinite loss exists for an investor who:（）

A. sells a put option.
B. buys a put option.
C. sells a call option.

单项选择题An analyst does research about well-function securities markets. In an informationally efficient securities market, does new information result in price adjustment that is:（）

A.A
B.B
C.C