I have been using TortoiseSVN, svn, and subclipse and I think I understand the basics, but there\'s one thing that\'s been bugging me for a while: Merging introduces unwante
In TortoiseSVN, you must only specify the revisions you want to merge. Unlike the command line client where you have to specify e.g. -r4:5 to merge the changes between r4 and r5, you only have to specify '5' as the revision number to merge in the TortoiseSVN merge dialog. If you're not sure, always use log dialog from the merge dialog and select the revisions you want to merge in that log dialog (then click OK and the selected revisions will automatically get set in the merge dialog).
As for resolving your conflict in TortoiseMerge: According to the screenshot in your question, TortoiseMerge shows you two conflicted lines (the ones shown as '????' in the bottom view). What you want is to include the change 'C' but not 'B'?