In DBMS the projection operation creates a new table that has less than or equal no. of tuples and less no. of attributes than the original table.

File locking is a mechanism that restricts access to a computer file, or to a region of a file, by allowing only one user or process to modify or delete it in a specific time and to prevent reading of the file while it's being modified or deleted.

Hamiltonian path is a path in a graph that visits each vertex exactly once.
So if each vertex is visited exactly once then to cover those vertices exactly n-1 edges are required,because if vertices are not repeated then edge will also be not repeated.

While the hierarchical database model structures data as a tree of records, with each record having one parent record and many children, the network model allows each record to have multiple parent and child records, forming a generalized graph structure.

The given sequence is,
4, 25, 15, 12, 20, 70, 40
Now let’s draw binary search tree for above sequence,

The post order traversal for above BST is,
12, 20, 15, 40, 70, 25, 4.

Selection sort algorithm involves minimum no. of records swap on an average and also in worst case. In selection sort the average or worst case no. of swaps is O(n).
Whereas in Bubble sort tha average no. of swaps is O(n^2) , in insertion sort it is O(n^2), and in quick sort it is O(nlogn).

Let check option wise,