高某，15岁，高中二年级学生，身高175，体重80kg，平时喜欢吃妈妈做的红烧肘子、

小儿惊厥使用水合氯醛镇静时最大剂量一次不超过( )。

A．5mg
B．10mg
C．5ml
D．10ml
E．20ml

明室覆片机是（）

A.晒版机械

B.冲洗底片机械

C.翻制底片机

D.间接版晒版机

甲烷爆炸极限为（）%。

A.5~15

B.2.75~28、6

C.2.3~9.5

D.2.7~8.5

掩护式液压支架执行元件的基本组成部分是（）等。

A、支柱

B、操纵阀

C、马达

D、平衡千斤顶

E、推移千斤顶

Both bus and tree topologies are characterized by the use of multipoint (71) ．For the bus，all stations attach，through appropriate hardware (72) known as a tap，directly to a linear transmission medium，or bus．Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the (73) ．A transmission from any station propagates the length of the medium in both directions and can be received by all other (74) ．At each end of the bus is a (75) ，which absorbs any signal，removing it from the bus．

A．tree
B．bus
C．star
D．ring