Which should be the correct answer for following question. If I consider Nexus I feel 'b' is correct choice.

I am not sure where this question came from, however, if there are multiple Scrum Teams working from a single Product Backlog (i.e. single Product) then dependencies should be minimized or eliminated as much as possible. This may be in the form of Product Backlog management or having the appropriate skills in the Scrum Team(s). This is one of the reasons why Backlog Refinement is an event in the Nexus framework.

Although I'm not in full agreement with the choices provided, based on my above explanation, and if I were to make a choice, I'd choose a.

'b' makes it sound like the SM is a PM, and 'c' implies you don't have a "Done" Increment.

During Sprints, a Development Team has to wait for another team to provide
some dependent input. Often this leads to delay in completing their work. What can be
recommended to this team?

How is this team visualizing their dependencies?

I'm curious as to what the source for this question is. I don't really like any of the answers.

Choice B introduces the concept of an SLA, which isn't defined in Nexus. Even so, such a definition would typically be more related to the time from starting work to delivering work. Unless there's close collaboration between the two teams, the team that is providing the dependent input may not be fully aware of the needs and dependencies. If they are, the work should be prioritized earlier, but starting it could depend on other work. All of these considerations point back to issues with dependency management.

Choice C also seems limited in applicability. Not all applications of Scrum and Nexus are in areas where sample input can be mocked up. Although this keeps the team teams busy on their work, there's also some risk where the team working on the dependent input may discover issues and need to change the input design, if there even was an input design agreed upon in advance.

Choice A seems to be the closest to what I'd consider correct, but it's not necessarily about cross-functional teams. Both teams could be fully cross-functional. It could be a case of dependency management. It's not clear why these two work items were pulled by different teams if there's a dependency. Regardless, I do think that it's correct for the Scrum Master to be involved in education regarding dependency management (including eliminating dependencies where possible) and cross-functional teams.

Out of these options, I'd choose A, but I'm not necessarily happy with it.

I'm going to select D) None of the above.  Even if I consider Nexus, I still say none of the above.  

This is an issue with the teams refinement.  An effective team wouldn't be puling in work that has unresolvable dependencies.  Any preparation would have been done ahead of time to mitigate the risk of dependencies.  And with those being known, the team would plan appropriately. In the case of the teams in the question, they didn't seem to have any plans in place to mitigate the risk of the dependency.  Adding more people to the team (option A) won't necessarily help especially if the problem has already caused issues.  Introducing SLAs (Option B) also is too late to help this situation and would not be effective going forward because each situation is unique.  Mocking up a sample (Option C) does nothing to show the work that has been done and invalidates any feedback that could be obtained in a review. 



There is no answer provided that I would select and I would highly question the value of the mock test you are looking at. 

Both A and B are alternative supplements that have occurred, not a good solution

C is no DoD delivery, nor is it the correct answer.

If there is a D, you should ensure that the team fully understands and uses the knowledge of Nexus

Which approach gives the Scrum Team the best opportunity of doing Inspect&Adapt?