前、后桅灯的垂向距离至少为（）。A.2m B.3m C.5m D.6m

根据首字母及文章大意完成下列短文

                                                             PEN PAL WANTED

     My (1)n__________ is Lei Tao, and my English name is Jack. I'm (2)__________

China. I (3)l__________ in Beijing, I (4)s__________ Chinese, I like sports very much.

(5)O__________ weekends,I go to play with my friends. Volleyball and football  are my

favorite (6)s__________. I (7)l__________ English class at school, because my English

teacher is very fun. I like math (8)t__________. My favorite (9)m__________ are action

movies and comedies. Jack Chan is my favorite actor. Please write and (10)t__________

me about yourself'.

合金刃具钢一般是（）。

A.低碳钢

B.中碳钢

C.高碳钢

D.高合金钢

热水采暖系统局部散热器不热的判别方法是用手摸两边管线温度，发现是否有明显的温差，确定位置后分析原因，并制定排除方案。

流脑主要经( )

A．飞沫传播
B．水、食物、苍蝇传播
C．吸血节肢动物传播
D．血液、体液、血液制品传播
E．土壤传播

已经掌握了“动物”这一概念，再学习“马”这一概念，属于

A．上位学习

B．下位学习

C．整合学习

D．并列结合学习