水泵叶轮相似定律的第二定律(扬程相似定律)，即H～n的关系为( )。 A．H/Hm

若承租方选择方案2，则其所支付租金的现值为( )万元。

A．55.52

B．56.52

C．78.36

D．68.18

酸和盐中的三种物质x、y、z，其中有两种元素相同，且这两种元素的质量比均为1：2，其转化关系如图所示：在①②③的转化关系中，一个有气体生成，一个有沉淀生成，一个有沉淀和水生成．则产生的气体可能是______，写出转化②的化学方程式______．

A little boy invited his mother to attend his school’s first teacher-parent meeting. To the little boy’s (1) , she said she would go. This (2) be the first time that his classmates and teacher (3) his mother and he felt (4) of her appearance. Although she was a beautiful woman, there was a severe sear (疤痕) that (5) nearly the entire right side of her face. The boy never wanted to (6) why or how she got the sear.At the meeting, the people were (7) by the kindness and natural beauty of his mother (8) the sear, but the little boy was still embarrassed (尴尬) and (9) himself from everyone. He did, however, get within (10) of a conversation between his mother and his teacher.The teacher asked (11) ," How did you get the scar on your face"The mother replied, " (12) my son was a baby, he was in a room that caught fire. Everyone was (13) afraid to go in because the fire was (14) , so I went in. As I was running toward his bed, I saw a long piece of wood coming down and I placed myself over him trying to protect him. I was knocked (15) but fortunately, a fireman came in and saved both of us. " She (16) the burned side of her face. "This scar will be (17) , but to this day, I have never (18) what I did. "At this moment, the little boy came out running toward his mother with tears in his eyes. He held her in his arms and felt a great (19) of the sacrifice (牺牲) that his mother had made for him. He held her hand (20) for the rest of the day.

第（1）空应选择（）

A．enjoyment     

B．disappointment 

C．surprise    

D．excitement

质量保证应当应用于：（）

A.抗HIV筛检

B.HIV抗原筛检

C.其它筛检项目

D.所有筛检项目