Which two instruments were noted to be fragile and easily damaged in early hearing aids?

The choice highlighting crystal microphones and receivers as fragile components in early hearing aids is accurate because both of these parts played pivotal roles in the functionality of early devices. Crystal microphones were often made from materials that could be easily damaged due to physical impact or environmental conditions, such as moisture and temperature fluctuations. Additionally, receivers, which are responsible for converting electrical signals back into sound, typically had delicate structures that were susceptible to failure if exposed to stress or mishandling.

In early hearing aids, advancements in technology were limited, resulting in components that were not as robust as those found in modern devices. The crystal microphone's reliance on fragile materials meant that small shocks or drops could lead to malfunction. Similarly, receivers had designs that made them vulnerable to wear and tear, which often hindered the overall performance of the hearing aid.

While other options presented components that may have different vulnerabilities or issues, crystal microphones and receivers specifically were known for their fragility, making this choice an accurate reflection of the historical context regarding the construction and durability of early hearing aids.