2014年10月10日，中欧论坛汉堡峰会在德国汉堡举行。国务院 * * 李克强发表演讲指出

Visitors to this country are normally admitted for six months, but foreign students can usually stay for one year. They must (51) an educational institution, and they are required to study for a minimum of fifteen hours a week on a (52) course. Prospective students have to show that they can afford their studies, and that they have sufficient (53) resources to support themselves (54) in this country.

In order to work here the foreigner needs a work permit, (55) must be applied for by his prospective employer. The problem here is that the Department of Employment has the right to grant or (56) these permits, and there is little that can be done (57) it; it would be extremely unwise for a foreign visitor to work (58) a permit, since anyone doing so is liable to immediate deportation (驱逐出境). There are some people from the Common Market countries, who are often given (59) residence permits of up to five years. Some other people, such as doctors, foreign journalists, authors and others can work without permits, and foreign students are normally allowed to (60) part-time jobs while they are studying here.

54().

A.after 

B.but 

C.while 

D.before

病毒的核酸有什么特点？

在申农一韦弗模式中，媒介被细分成（）

A.发射器

B.信源

C.信道

D.接收器

E.信宿

某建筑企业2010年初房产原值为9400万元，本年房产使用及变动情况如下：
(1)4月对原值为1500万元的办公楼的中央空调进行更换，更换的新的中央空调价值100万元，更换掉的旧空调价值40万元，已提折旧36万元；更换易损的照明设备，新的照明设备价值0.8万元，更换掉的旧照明设备价值0.2万元，4月末更新完毕。
(2)6月9日将去年自建的原值为600万元的厂房转让，取得销售收入720万元，该厂房的建造成本为260万元，已提折旧120万元。
(3)9月5日，购进新建的商品房作为职工宿舍，该宿舍于10月10日交付使用，原值2400万元。
(4)4月1日开始对原值为2000万元的厂房进行大修，10月大修完毕，10月底交付使用，原值增加了300万元。
其他材料：计算房产余值时的扣除比例为30%，厂房的成本利润率为15%。
要求：根据上述资料，按照下列序号计算回答问题，每问需计算出合计数。

2010年该企业年更换空调的办公楼应缴纳的房产税；

请写出差压变送器密封性检查方法并画出实验系统图。