Final answer:
In superheterodyne receivers, oscillators must be highly stable to ensure accurate frequency conversion and proper functioning. Unstable oscillators lead to frequency drift and reception problems. Therefore, the oscillators in these receivers are prioritized for their stability.
Step-by-step explanation:
The oscillators contained in a superheterodyne receiver must be highly stable. Stability in oscillators is crucial for maintaining the correct frequency conversion necessary for superheterodyne receivers to function accurately. These receivers mix a received signal with a precise local oscillator frequency to create an intermediate frequency (IF) that is easier to filter and amplify.
In a superheterodyne receiver, the importance of oscillator stability cannot be overstated as it affects the selectivity and sensitivity of the entire receiving system. An unstable oscillator would result in frequency drift, which can lead to incorrect tuning and reception issues. Therefore, the correct answer is 'd. Highly stable'. In contrast, option 'a. Unstable' would cause undesirable reception and tuning performance, while the terms 'low frequency' and 'high frequency' relate more to the range at which the oscillator operates, rather than its stability.