慢性乙型、丙型肝炎抗病毒治疗的目的是（） A.抑制病毒复制直至病毒被清除 B.恢

PbSO₄是一种难溶于水和强酸的盐。若将PbSO₄固体加入醋酸铵溶液中，能够得到澄清溶液A；若向A中通入H₂S气体，又会得到黑色沉淀B和具有一定酸性的溶液C。试回答：

(1)A溶液中的溶质是什么？写出化学式__________________。

(2)写出PbSO₄溶解的离子反应方程式__________________。

(3)B的化学式是________，并写出生成B的离子反应方程式_________________________________。

(4)C溶液中溶质的化学式为_________。(假设每步离子反应都恰好完全反应)。

下腔静脉阻塞综合征所致的水肿的主要机制是

A.血浆胶体渗透压下降

B.组织压增加

C.毛细血管内静水压增加

D.淋巴回流受阻

E.血管通透性增加

慢性肺心病的发生过程中，以下不是导致肺动脉高压重要因素的是（）.

A.肺血管解剖结构改变

B.缺氧

C.电解质紊乱

D.血液黏度增加

E.血容量增高

Visitors to Britain may find the best place to sample local culture is in a traditional pub. But these friendly hostelries can be minefields of potential gaffes for the uninitiated.
An anthropologist and a team of researchers have (1) some of the arcane rituals of British pubs—starting with the (2) of getting a drink. Most pubs have no waiters—you (3) to go to the bar to buy drinks. A group of Italian youths (4) for 45 minutes before they realized they would have to (5) for their own. This may sound inconvenient, but there is a (6) purpose.
Pub culture is designed to (7) sociability in a society known for its reserve. Standing at the (8) for service allows you to chat with others (9) to be served. The bar counter is possibly the only (10) in the British Isles in which friendly conversation with (11) is considered entirely appropriate and really quite normal (12) . "If you haven’t been to a pub, you (13) been to Britain." This tip can be found in a (14) , Passport to the Pub: The Tourists’ Guide to Pub Etiquette, a (15) code of conduct for those wanting to sample "a central part of (16) life and culture". The trouble is that if you do not (17) the local rules, the experience may fall flat. For (18) , if you are in a big group, it is best if only one (19) two people go to buy the drinks. Nothing irritates the (20) customers and bar staff more than a gang of strangers blocking all access to the bar while they chat and dither about what to order.

如何判断碱液受污染？