Changes to Sprint Backlog

Hi,

I wanted to clarify my understanding of: changes to Sprint Backlogs.

As per my understanding, once the subset of User Stories (items) are selected from the Product Backlog, this now forms the scope of the Sprint Backlog. Once the Sprint Backlog is finalised, no new User Stories can be added to the Sprint Backlog.

In online quizzes i have got the following questions wrong:
1. Is it prohibited to add new work into the Sprint Backlog later by the Development Team?
I answered True (but the correct answer was False).

My Question: By "Work", does that mean "Tasks"? If so, I understand why the answer is False.

2. Who is allowed to make changes to the Sprint Backlog during the Sprint?
I answered "No-one", but the correct answer was "Development Team".

My Question: I thought that once the Sprint Backlog was finalised no changes could be made? Or are they referring to reducing Sprint Backlog scope only?

Thanks