$A$ narrow but tall cabin is falling freely near the earth's surface. Inside the cabin,two small stones $A$ and $B$ are released from rest (relative to the cabin). Initially $A$ is much above the centre of mass and $B$ is much below the centre of mass of the cabin. $A$ close observation of the motion of $A$ and $B$ will reveal that

• A
  both $A$ and $B$ continue to be exactly at rest relative to the cabin
• B
  $A$ moves slowly upward and $B$ moves slowly downward relative to the cabin
• C
  both $A$ and $B$ fall to the bottom of the cabin with constant acceleration due to gravity
• D
  $A$ and $B$ move slightly towards each other vertically