Explanation: In a Class A amplifier, grid bias establishes the quiescent (no-signal) operating point, ensuring the active device (like a vacuum tube) operates in its linear region for the entire 360-degree input signal cycle. 1. **Distortion of the output waveshape (A):** If the grid bias is incorrect, the amplifier will operate outside its linear region. If biased too close to cutoff, the negative peaks of the signal will be clipped. If biased too close to saturation, the positive peaks will be clipped. In either case, the output waveform no longer faithfully reproduces the input, resulting in distortion. 2. **Possible excessive plate dissipation (B):** If the grid bias is too low (i.e., not sufficiently negative for a vacuum tube), the quiescent plate current will be excessively high. Plate dissipation is the power consumed by the plate, primarily due to the plate current flow. A high idle current can cause the plate dissipation to exceed the device's maximum ratings, leading to overheating and potential damage. Since incorrect grid bias can cause both waveform distortion and excessive plate dissipation, both A and B are correct, making C the comprehensive answer.