Which of the following can lead to interference in signal performance?

Interference in signal performance can be caused by various factors that affect the integrity and clarity of the transmitted signal. Static discharge and ground loops are significant contributors to such interference. When static discharge occurs, it can introduce unwanted electrical noise into the signal pathway, disrupting the intended transmission. Ground loops can create multiple grounding points within an AV system, leading to varying ground potentials, which can cause hum and noise in audio and video signals.

While external electrical devices and physical obstructions can also contribute to interference, they are not the sole or singular causes. External devices can introduce electromagnetic interference, and physical obstructions can attenuate signals, but the options presented do not solely represent their effects. Therefore, static discharge and ground loops are highlighted as critical considerations because they are common issues that directly impact signal integrity and can occur in a variety of environments.

In summary, static discharge and ground loops represent direct and prominent reasons for signal interference, making them the most significant factors in the context of the provided options.