There are fewer teaching positions left in big cities, ____ at the same time there are shortages of teachers in

small towns. [ ]

A. or

B. and

C. so

D. for

男性，40岁，3小时前突然出现剧烈头痛，伴呕吐。查体：颈部轻度抵抗，克氏征阳性，体温37．5℃，血压17．5／10．7kPa。其他神经系统检查阴性，诊断首先考虑（）

A.偏头痛发作

B.脑出血

C.脑炎

D.蛛网膜下腔出血

E.脑神经纤维瘤