When performing a drag-and-drop Replace Edit to the Program Monitor without a clip selected in the sequence, Premiere Pro's behavior is context-dependent on the playhead's position. The action specifically targets the clip that is currently under the playhead on the source-patched track. If a clip is present at this location, it will be replaced by the source clip. The duration of the new clip will be trimmed to match the duration of the clip it is replacing. If there is no clip under the playhead on the targeted track, the operation is aborted, and no edit occurs.

A. This describes an edit initiated by a sequence In point, which is not the primary targeting method for a Replace edit when no clip is selected.

B. This describes a standard Overwrite edit. A Replace edit requires an existing clip to replace, whereas an Overwrite edit does not.

D. The presence of sequence In or Out points is not a requirement for this specific type of Replace edit to function; the sole condition is a clip under the playhead.

1. Adobe Premiere Pro User Guide

"Add clips to sequences" section. Under the subsection "Replace a clip in a sequence

" the documentation states: "If no clip is selected in the Timeline panel

Premiere Pro replaces the clip at the playhead on the targeted track." This directly supports the logic that the edit is contingent on a clip being present at the playhead. (Source: Adobe HelpX

Premiere Pro User Guide

Add clips to sequences).

2. Adobe Premiere Pro User Guide

"Drag-and-drop edits" section. This section details the various drop-zones in the Program Monitor. The "Replace" zone's function is described as replacing the contents of an existing clip in the timeline. This reinforces that its primary function is to act upon an existing clip

which

in the absence of a selection

is the one at the playhead. (Source: Adobe HelpX

Premiere Pro User Guide

Drag-and-drop edits).