Which of the following statements about selling shares of stock is FALSE（）

A. The "depth" of the market is typically defined as the number of traders willing to trade at prices above and below the current price.

B. If the initial margin requirement is 50% and the maintenance margin requirement is 25%, the investor who buys a stock at $26 on margin will receive a margin call when the stock hits $17.33.

C. Initial public offerings are sold in the secondary market.

目前世界各国生产的火灾探测器不包括( )类型。

A．感烟火灾探测器

B．感声火灾探测器

C．感温火灾探测器

D．复合式火灾探测器