Final answer:
An E1 circuit has 32 channels, but typically only 30 are available for voice, video, or data, as two are reserved for network management purposes.
Step-by-step explanation:
The question relates to the number of channels available on an E1 circuit for use with voice, video, or data communications. An E1 line provides a total of 32 channels. However, not all of these channels are available for regular voice or data transmission as one channel (channel 0) is reserved for framing and synchronization, and usually, another channel (channel 16) is reserved for signaling, leaving us with 30 usable channels. So the correct answer is a) 32 channels, but with the caveat that typically only 30 are available for voice, video or data as the other two are used for network management purposes.