根据《建筑安装工程费用项目组成》(建标(2003)206号)文件的规定，已知某材料供

检修门、井道安全门及检修活板门均应向井道内开启，且应有用钥匙开启的锁。()

如图B5-3所示架空隔热屋面上的w值，何者正确（）

A. ≤100mm

B. 150mm

C. 200mm

D. ≥250mm

司机做好其它检查工作后，认真试车、起落大钩一、二次，大、小车往返开动几次，注意察听（）、（）的运转声音是否正常。

Which of the following is least accurate regarding product development and marketing for firms under monopolistic competition（）

A. Firms that bring new and innovative products to the market face relatively more elastic demand curves than their competitors.

B. Relative to other types of competition, product innovation is critical to the pursuit of economic profits.

C. Advertising is necessary to communicate the uniqueness of the firm’s products relative to its competitors.

什么是柱塞有效行程？