Length of a scrum project

What do you think is the correct answer and why?

I am really unsure! Time should not be too long to develop as the need could have gone, so I would not go for 1 year. it cannot be fix as user experiences that need to be fulfilled will be different. So always 2 weeks or 1 sprint should not be right either. 1 Sprint is fixed as well and doesn't apply either. 

Non of them?

Have a read of the Scrum Guide http://www.scrumguides.org/scrum-guide.html

There are a few key things in there that should help you grasp the question and the answer.  For example, A Product Backlog is never complete.

If the question is "What can be the length of a scrum project?", then perhaps a better way to word the question would be to break it up:

• Can a project be a single sprint?
• Can a project consist of multiple sprints?

Although I do also want to point out that having "None of the Above" placed above "All of the Above" is poor test formatting, which may confuse ESL test takers.

I would highly question any testing source that believes there are such things as Scrum projects.

As stated already in this thread, a Product Backlog is a living, evolving entity.   Projects inherently have a beginning and an end; therefore, projects do not apply when discussing Scrum.

Scrum is agnostic about the concept of a project. A Sprint might be a project to a Scrum Team.

It would be fairest to say that Scrum does not prescribe the use of "projects", or otherwise utilize them as a vehicle for delivery.