antonTobi: After B2-B3, black should pass rather than add a move at D2 (assuming Japanese rules). But it's still one point worse than starting at B3, right? So it seems misleading that they're both marked as correct :)
Sadaharu: Even if Black doesn't play D2, black still has only 8 points because white can force black to take 4 stones by playing at C1 or B2 eventually. B3 also has 8 points. Original answer only had B2 but I found out that B3 also works so I kept both since they both win
Yeah, the author thought that B3 doesn't work but I think he missed out that black can connect first instead of taking the ko.