C

Step 1: Understanding the fields around a charged particle.
When dealing with charged particles such as electrons, they produce an electric field due to their charge. This electric field is independent of the observer's state of motion.

Step 2: Considering the motion of the observer.
If the observer is moving with respect to a stationary electron, this relative motion changes how the electric field is perceived. According to the theory of electromagnetism, a moving charge creates both an electric field and a magnetic field in the reference frame of the observer.

Step 3: Application of electromagnetism principles.
The presence of a moving observer relative to a stationary charge (the electron) implies the observer will experience a Lorentz transformation of the electric field, thus observing a magnetic field as well. Both the electric and magnetic fields are intertwined due to this relative motion.

Conclusion: Therefore, the observer will observe both the electric field and a magnetic field. Hence, the correct option is C: Both.