为了保持环境中空气的新鲜和清洁，下列哪项做法欠合理？ [ ]
A．绿化环境
B．保持室内空气流通
C．室内多放些绿色植物
D．保持环境卫生和个人卫生
答案：C
改变结焦时间或改变标准温度时，应该加测焦饼中心温度。
IPv6 is short for "Internet Protocol Version 6". IPv6 is the "next generation" protocol designed by the IETF to ( 71 ) the current version Internet Protocol,IP Version 4("IPv4"). Most of today’s Internet uses IPv4, which is now more than twenty years old． IPv4 has been (72) resilient in spite of its age, but it is beginning to have problems. Most importantly, there is a growing ( 73 ) Of IPv4 addresses，which are needed by all new machines added to the Internet.IPv6 fixes a number of problems in IPv4，such as the (74) number of available IPv4 addresses. It also adds many improvements to IPv4 in areas such as routing and network autoconfiguration.IPv6 is expected to gradually replace IPv4，with the two coexisting for a number of years during a transition (75) .
A．days
B．period
C．phase
D．epoch
