D

Step 1: Understand that electric potential (V) is defined as the potential energy (U) per unit charge (q). It can be expressed as $V = \frac{U}{q}$.
Step 2: For an object with a positive charge, the electric potential at that point can vary depending on the surrounding charges and the configuration.
Step 3: If the object is isolated, it can only contribute to a potential that is positive. However, if it is near other charges, such as a negatively charged object, the potential at the location of the positively charged object can be influenced by those charges.
Step 4: The potential can thus be positive, negative or zero based on the relative positions and magnitudes of other charges nearby.
Therefore, the correct answer is D: may be positive, negative or zero.