Dropping at C would have been a loss of hole in match play, 2-stroke penalty in stroke play.
In golf, the ball must be played as it lies in it's final at rest position, unless taking relief. When taking relief, in this case from ground under repair, first mark your ball (you may now clean it if you like, unless taking relief from a hazard). Then determine which club you would use from the original lie, if it was to be played (i.e., likely your chipping iron from A) and lay it 90 degrees or more (never closer to the hole) to the pin. Never remove the marker for your original lie until you've determined the nearest point of relief. Take your line to the right until you've gained one club length of relief for stance and swing, and place a mark. Take your line to the left until you've gained one club length (still the original club) and make a mark (tees normally). Whichever mark is closest to A is your nearest point of relief. If those flower beds are considered a part of the course (which they normally are---local rules may hold different stipulations for ball in the flower beds) and your nearest point of relief was in them, you would have to drop in the bed and play it as it lies (D or E below) or declare it unplayable and take two club lengths relief, plus a penalty (plus a stroke for each additional two clubs to get out of the beds). After all is said and done you take your drop standing directly behind your nearest point of relief marker perpendicular to the pin. After your round you politely inform the course manager that the area was unclearly marked and you failed to observe a drop zone (which there normally is for this type of situation near the green. When a drop zone is marked off, you always take your drop there, regardless of where your nearest point of relief may have been.
So, a lot to explain so little:)
If you were just dying to be lying below the pin you could claim the cart path as your initial nearest point of relief, and then take relief from the path, but F below is the best you can do (again, as long as the beds are out of play).
Just remember, if where you drop is closer to the pin than where you started, or farther away from where you could have dropped (even though less desirable), your cheating. I'd've taken B rather than play over the sand at F, and if B and C really were both equidistant and neither advanced my ball, take the more difficult play---then there is no doubt.