Suppose you are given an implementation of a queue of integers. The operations that can be performed on the queue are:
i. isEmpty (Q) — returns true if the queue is empty, false otherwise.
ii. delete (Q) — deletes the element at the front of the queue and returns its value.
iii. insert (Q, i) — inserts the integer i at the rear of the queue.
Consider the following function:

void f (queue Q) { 
  int i ; 
  if (!isEmpty(Q)) { 
      i = delete(Q); 
      f(Q); 
      insert(Q, i); 
  } 
} 

What operation is performed by the above function f ?

Consider the B⁺ tree in the adjoining figure, where each node has at most two keys and three links.

Keys K 15 and then K 25 are inserted into this tree in that order. Exactly how many of the following nodes (disregarding the links) will be present in the tree after the two insertions?

The order of a leaf node in a B⁺- tree is the maximum number of (value, data record pointer) pairs it can hold. Given that the block size is 1K bytes, data record pointer is 7 bytes long, the value field is 9 bytes long and a block pointer is 6 bytes long, what is the order of the leaf node?

Consider the B⁺ tree in the adjoining figure, where each node has at most two keys and three links.

Now the key K 50 is deleted from the B⁺ tree resulting after the two insertions made earlier. Consider the following statements about the B⁺ tree resulting after this deletion.

i) The height of the tree remains the same.

ii) The node (disregarding the links) is present in the tree.

iii) The root node remains unchanged (disregarding the links).

Which one of the following options is true ?