Final answer:
The purpose of cache is to reduce traffic on the access link, thereby making efficient use of existing bandwidth and helping to reduce redundant data requests over the network.
Step-by-step explanation:
The purpose of cache is to reduce traffic on the access link, which answers the question from the options provided. Cache is a hardware or software component that stores data so future requests for that data can be served faster. The data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere.
A cache does not inherently increase bandwidth on the access link; instead, it allows for the more efficient use of the existing bandwidth by reducing the number of times data must be fetched from the original source. This can lead to perceived faster response times for the user but does not increase the actual bandwidth of the connection.
Furthermore, by storing frequently accessed data locally on the network or in the computer, some redundancy in data requests can be eliminated, effectively reducing bandwidth usage on an access link as repetitive information does not need to be sent across the network each time it is needed. Therefore, option b) 'Reduce traffic on access link' would be the most appropriate answer.