The correct answer is D. the height of the object.
Gravitational potential energy (GPE) is calculated using the formula:
\[ \text{GPE} = mgh \]
where \( m \) is the mass of the object, \( g \) is the acceleration due to gravity (the strength of the gravitational field), and \( h \) is the height of the object above a reference point. The shape, temperature, and velocity of the object do not directly affect its gravitational potential energy.