上海世博会园区80%的夜景照明光源采用低碳节能的LED(发光二极管)照明技术。制作 LED 灯的核心材料是: [ ]
A、导体
B、半导体
C、绝缘体
D、超导体
答案:B
________ other children, the father thinks, Jack is ______ son.
A.Compared with; the most satisfied
B.Comparing to ;the most satisfied
C.Comparing to; a most satisfied
D.Compared with; a most satisfying
按《建筑桩基技术规范》(JCJ 94—1994)规定进行桩径大于~600灌注桩施工,在开始灌注水下混凝土时,导管底部至孔底的距离宜为下列()组范围值。
A.300~500 mm
B.500~800 mm
C.800~1000 mm
D.1000~1200 mm