The correct option is Rebase then fast forward merge.

Rebase then fast forward merge reapplies the feature branch commits on top of the target branch and then advances the branch pointer without creating a merge commit. This preserves each original commit and produces a strictly linear commit graph without merge nodes.

Merge without fast forward is incorrect because it forces a merge commit even when a fast forward is possible and therefore adds merge nodes to the history.

Squash merge is incorrect because it collapses all branch commits into a single commit which loses the separate commits. Even though it avoids merge commits it does not preserve the original, per commit history that a team might require.

Rebase then create a merge commit is incorrect because creating a merge commit reintroduces a merge node into the graph and so the history is not strictly linear.

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