Question 1057231
It's ambiguous.  It clearly cannot be c or d, because they aren't quadratic.
The scale for a assumes the first data element is year 1.
The scale for b assumes the first data element is year 8, which would fit if the 0 period were 1990.  I like b better for that reason. I don't like year 1 for the first element, because it suggests there is a year 0, which I don't see.