Imagine a situation where 2 developers are simultaneously modifying 3 different software components. What difficulties might arise when they try to merge the changes that they have made?

What will be an ideal response?

There is the usual problem where developers each make changes to the same
component and these changes are, in some way, incompatible. However, where
several components are being changed at the same time, the problems are
exacerbated because there may be dependencies between the components that are
affected by the changes. For example, say developer A checks out components X
and Y and decides to implement a change by changing Y, which depends on a
particular feature of X. Developer A checks X and Y back in with no changes
recorded as being made to X. Developer B also is working on X and Y and changes
both X and Y. However, the changes made to X mean that the assumptions made
by Developer A no longer hold. However, incompatibility is not detected as there
has only been a single change made to component X.
With more than 2 components, the problem becomes even worse because of
the chains of dependencies that can be introduced. These can be very difficult or
impossible to detect automatically.