Q20

[ManhattanPrepLSAT1]

If one set of line 2 tickets is green that set will have to be the set in February. No more February tickets can be green so the green tickets for line 3 will need to be in January. That forces the red tickets in January onto line 1. Since line 1 tickets in February cannot be red, they will have to be yellow, forcing red tickets into line 3 for February.