假定X和Y两种产品有线性无差异，其斜率是1/2，即MRSxy=1/2，问：当Px=1

– Amazing! You _____ have won the first prize in the national English speech contest!

– I’m lucky that all my efforts have finally paid off.  

A．must

B．may

C．can

D．should

For (1) service, we need a virtual-circuit subnet. Let us see how that works. The idea behind virtual circuits is to avoid having to choose a new  (2) for every packet sent. Instead, when a connection is established, a route from the  (3) machine to the destination machine is chosen as part of the connection setup and stored in tables inside the (4) .That route is used for all traffic flowing over the connection, exactly the same way that the telephone system works. When the connection is released, the virtual circuit is also terminateD. With connection-oriented service, each packet carries an  (5) telling which virtual circuit it belongs to.

空白（5）处应选择（）

A.address

B.identifier

C.interface

D.element

与无线终端正在连接，且不是HA的无线控制器，该无线控制器即为它的（）。

男性，4岁，自幼人工喂养，形体明显消瘦，肚腹膨胀，青筋暴露，毛发稀疏，色黄结穗，精神不振，咬指磨牙，近一个月来，全身、目胞、四肢浮肿，面色无华，小便短少，舌质淡嫩，苔薄白。

此患儿如果出现肿满虚浮，按之如泥，小便清，夜尿多，为脾病及肾，肾失气化，宜选方剂是（）

A.桑螵蛸散

B.巩提丸

C.金匮肾气丸

D.菟丝子散

E.缩泉丸

关于电力变压器的励磁电抗，下述说法中错误的是（）

A、不管电力变压器的类型和绕组接线方式如何，其正序励磁电抗和负序励磁电抗都可以视为无限大

B、不管电力变压器的类型和绕组接线方式如何，其零序励磁电抗都可以视为无限大

C、对于三相组式变压器，其正序励磁电抗、负序励磁电抗和零序励磁电抗都可以视为无限大

D、当三相变压器包含有三角形接线绕组时，不管变压器的类型如何，其零序励磁电抗都可以视为无限大