搜题请搜索小程序“爱下问搜题”
问题 单项选择题

正常心脏的胚胎发育中，心前细胞出现并心脏开始发育至形成四腔胎儿心脏止，经历时间约为（）

A.15天

B.20天

C.1个月

D.2个月

E.3个月

答案

参考答案：C

解析：从胚胎的第3周中期，心前细胞出现并心脏开始发育至形成四腔胎儿心脏止，总共历时约1个月。

问答题

A．Why she should tell her students about her plans.

B．What he plans to do when he’s on sabbatical.

C．Why she can’t take a sabbatical next semester.

D．Why her students probably weren’t surprised by her announcement.
查看答案
材料分析题

所谓“低碳经济”是以低能耗低污染，低排放为基础的经济模式，是人类社会继农业文明，工业文明以后的又一次重大进步，我国政策重视发展低碳经济，指导居民过低碳生活，目前国外在发展低碳经济中有许多成功之处，我国可以借鉴。

（1）上述材料体现了我国哪些基本国策？

                                                                                                                                                               

（2）就居民消费而言，举两例来响应党和国家提出的低碳生活

                                                                                                                                                              

                                                                                                                                                               （3）大力发展低碳经济，彰显着实施可持续发展战略重要性，试简述我国实施可持续性发展战略的原因。

                                                                                                                                                              

                                                                                                                                                              

（4）我国实施可持续发展战略，努力实现的社会目标是什么？

                                                                                                                                                              

                                                                                                                                                              

查看答案