I beg to differ. Option d) is the only correct answer.
c) If we have to implement a Queue of size \(n\), a linked list representation needs space for both pointers and data. But an array just needs data space.
Note: We are asked to implement a Q of size \(n\), and not told to find out the space efficiency when the Q is only partially full.
d) If we need to implement multiple Queues, that need to hold n elements in total, using a linked list representation allows the lists to grow and shrink independently. So, if one Queue is completely full, the others can still be of length \(0\).
However, if we use an array, and we do not know how the input will be distributed among the Queues behore-hand, we will have to make all the Queues of capacity \(n\). So, even though we will be storing \(n\) elements in total, we will be allocating \(n \times k\) space (\(k\) is the number of lists that need to be implemented).