二战后,导致发展中国家出现局部战争的外部因素是 A．领土纠纷 B．民族、宗教矛盾

乳糜泻病人与下列哪种HLA抗原呈关联（）

A.HLA-B₁₇

B.HLA-B₈

C.HLA-DR₂

D.HLA-DR₃

E.HLA-B₃₅

如图所示，一束极细的可见光照射到金属板上的A点，可以从A点向各个方向发射出速率不同的电子，这些电子被称为光电子．金属板左侧有一个方向垂直纸面向里、磁感应强度为B，且面积足够大的匀强磁场，涂有荧光材料的金属小球P（半径忽略不计）置于金属板上的A点的正上方，A、P同在纸面内，两点相距L．从A点发出的光电子，在磁场中偏转后，有的能够打在小球上并使小球发出荧光．现已测定，有一个垂直磁场方向、与金属板成θ=30°角射出的光电子击中了小球．求这一光电子从金属板发出时的速率v和它在磁场中运动的可能时间t．已知光电子的比荷为

边墙基底以上1m范围以外超挖大于规定时可用（）回填密实。

A、片石混凝土；

B、10号浆砌片石；

C、石渣回填捣实。

Increasingly, the development of tourism is seen to have an effect on the environment. Erosion (磨损) is one problem. The steps and stones of major popular (51) like Shakespeare’s birthplace or Stonehenge (巨石阵) are literally being worn away by millions of foreign feet. The (52) in the case of Britain’s best known prehistoric monument has been to use railings to keep visitors at a distance. Such measures can hardly be (53) in the house of the Bard, however, where tourists want to enter the actual building.

Overcrowding in cities, towns and villages is (54) problem. Traffic jams are an outcome. In narrow roads, tourist vehicles cause congestion. (55) traders and residents cannot get around to do their work. Car parks fill up, (56) strangers park their cars where they can: in streets, across gateways, in lay-bys, or even in (57) driveways. This causes obstruction. The sheer weights of in-comers can be a hazard. Thus Venice, a city built for half a million inhabitants, is (58) by another half million who populate the city daily in the tourist (59) —eight million visits each year. The mayor recently decided to (60) visitors to 90,000 a day. the only way to save the city from overcrowding.

54().

A. second

B. another

C. other

D. the other