As a wave propagates [IIT-JEE 1999]

• A.            The wave intensity remains constant for a plane wave
• B.            The wave intensity decreases as the inverse of the distance from the source for a spherical wave
• C.            The wave intensity decreases as the inverse square of the distance from the source for a spherical wave
• D.            Total intensity of the spherical wave over the spherical surface centered at the source remains constant at all times