The object with the greatest gravitational attraction toward the center of Earth is the one with the greatest mass. The options provided are:
- a 3-kilogram bag of rice
- a 0.4-kilogram book
- a 400-kilogram roller coaster car
- a 1,500-kilogram truck
Among these options, the 1,500-kilogram truck has the greatest mass, and therefore it has the greatest gravitational attraction toward the center of the Earth.