Solution :
Acceleration due to gravity of the earth, g 

Acceleration due to gravity at 1000 km depths is :




= 8.23 m/s
Acceleration due to gravity at 2000 km depths is :




= 6.73 m/s
Acceleration due to gravity at 3000 km depths is :



= 5.18 m/s
Acceleration due to gravity at 4000 km depths is :




= 3.64 m/s
The dimensions of the completed ISS research facility will be approximately 356 feet (109 meters) by 240 feet (73 meters), or slightly larger than a football field. the ISS weighes around 450 tons (408,000 kg), or 450 times the weight of an average car.
The answer is B. A frame of reference that is accelerating.