题干
28. The Hotel Al Arab, ______ the first and only 7-star hotel in the world, was designed in the shape of a sail of 321 meters.
A：having been considered
B：considering
C：being considered
D：considered
答案(点此获取答案解析）
D
速度由左边界的O1点射入磁场、电场区域，恰好沿直线运动到区域右边界的O2点（图中未标出）穿出。若保
持磁场强弱、方向和电场方向不变，只增大电场强度大小，另一个同样的粒子b（不计重力）仍以相同初速度由O1点射入，仍然能
够从区域右边界穿出，则粒子