The question is a easy one. What you must do is, to device an algorithm to make bi-partite graph.

A sure-shot algorithm is this-

Checking if a graph is possible or not can be done in O(1) time.

If its possible-

First make d edges to satisfy minimum degree. I did it by giving edges like, 1 to 1, 1 to 2, 1 to 3…1 to d. Then 2 to 2, 2 to 3, 2 to 4…2 to d+1. In case we exceed n, we take %n. Eg, edges of n-1 are - n-1 to n-1, n-1 to n, n-1 to 1, n-1 to 2… and so on till d edges.

Now for every remaining edge, take a vertex and give it as many edges as you can. Eg- Lets take vertex 1 for example. We gave edges of 1 to 1, 1 to 2,…1 to d. Now we will give it as many edges as possible, i.e. 1 to d+1, 1 to d+2, …1 to D. We stop when either there are no more edges, or 1 gets degree D. If 1 gets degree D and more edges remain, we simply go to next vertex and carry on. Eg- lets say 1 got degree D. Now we come at vertex 2. It had edges 2 to 2, 2 to 3…2 to d+1. We give edges in pattern 2 to d+2, 2 to d+3…2 to D+1. (Note- If you add edges in way like 2 to 1, then 2 to d+1, 2 to d+2… then it will give WA, because in cases you will exceed D for vertex 1 this way. Its crucial to start adding vertex from where we left off after satisfying the degree d.)

Code- https://www.codechef.com/viewsolution/15537558