实行行政首长负责制这一重大地方政府组织结构变革出现在我国什么时期？（）A、人民政府委

阅读下面短文，根据一下提示：1）汉语提示；2）首字母提示；3)语境提示，在每个空格内填入一个适当的英语单词，并将该词完整地写在右边相对应的横线上。所填单词要求意义准确，拼写正确。

Dear Jenny,

In your letter , you asked me something about how to

Keep  healthy. Here are my tips. First______all, try to

keep a _______(平衡) diet. Every day, you’d better eat

different kinds of food,___________as fish, meat and beans,

e__________fresh vegetables and fruits . Also, do remember

not to eat too much____________(糖)for your age. Secondly,

t__________regular exercise is necessary to you. You can do

sports which_______(适合)yourself , like running and

swimming . Thirdly, be sure that you have p_________of

sleep . Never stay up late . F__________, always be optimistic

about anything unlucky ___________comes your way so you

can stay in a good mood for the challenges in life.

Best wishes!

Yours,

Li Hua.

一个力的存在，离不开______和______，如人踢球，脚给球一个向前的推力，这个力的施力物体是______，受力物体是______；由于力的作用是______，所以脚给球施力的同时，受到了球给脚的______．

细胞间信号分子——化学信号的特点？

窦房结

A．结内为神经细胞
B．其功能是传导冲动
C．位于下腔静脉与右心耳交界处的心外膜深面
D．为心的正常起搏点
E．通过房室束将冲动传至房室结

试述纤维性能对非织造材料性能的影响。