构成：am/is/are (not) + being + V-过去分词
用法：
1、表现正在进行或发生的被动动作，常与now, look等词连用。
e.g.She is being examined by the doctor now.
2、表示现阶段或目前这段时间正在进行的被动动作，但这一被动动作在此时此刻不一定正在发生。
e.g.A new factory is being built.
They are being taught English at present .