目前常用的圆柱形电离室气腔长度最大为（）
A.2mm
B.5mm
C.10mm
D.20mm
E.25mm
参考答案：E
— How many do we need?
— ______.[ ]
A. tomatos; Only one
B. honey; One teaspoon
C. tomatoes; Just a few
D. honey; Two teaspoons
425+683+544+828的值是( )
A．2480
B．2484
C．2486
D．2488
