[单选] 矿山企业的主要负责人每月带班下井不得少于（）个。

Which two are characteristics of the cost-containment business challenge?（） reducing security breaches。 using the Internet more。 reducing upgrade charges。 adopting new applications and service。 银行的自有资金包括资本金、（）、（）和未分配利润等。 简述西洋参的功效与作用。 下列哪个不是人际交往的功能（） 心理保健。 行为协调。 展示个人魅力。 avoid Layer 2 loops. Which two of the following are most probably the reasons for that preference?（） Information about port roles is sent to all switches.。 RSTPs that are based on Cisco products require no additional configuration.。 Features such as UplinkFast and BackboneFast are compatible with RSTP.。 An RSTP that is based on Cisco products generally performs better than the Cisco proprietary 802.1D enhancements.。 矿山企业的主要负责人每月带班下井不得少于（）个。