Final answer:
Mass is responsible for the creation of a gravitational field around an object. Gravitational fields diminish with distance from the object's center and are a key aspect of explaining forces in physics.
Step-by-step explanation:
The cause of a gravitational field around an object is B. Mass. Every object with mass creates a gravitational field in the space around it. This gravitational field can be described as a vector field which means it has both a magnitude and a direction. For a spherically symmetric object with mass, the gravitational field is radial and diminishes with the square of the distance from the object's center. Notably, gravitational mass, which is responsible for the gravitational interaction, is experimentally found to be the same as inertial mass, which resists acceleration. These properties support conservation principles and are a key component in explaining how forces act upon objects within inertial reference frames.