How can a user exchange one clip in a sequence for another clip in the Project panel? 

Drag and drop the clip from the Source monitor onto the clip segment in the sequence while holding the Alt (Windows) or Option (Mac OS X) key 

Drag and drop the clip segment in the sequence onto the new clip in theProject panel 

Drag and drop the clip segment in the sequence onto the new clip in the Source monitor 

Drag and drop the clip from the Source monitor into the Program monitor while holding the Ctrl (Windows) or Command (Mac OS X) key