Places Like La Venta, San Lorenzo, and Laguna De Los

Places like La Venta, San Lorenzo, and Laguna de los Cerros likely became important centers because:

A) rich farm land produced surplus wealth concentrated in the hands of a few
B) of their location near the extremely valuable basalt sources in the Tuxtla Mountains
C) of their proximity to the large urban centers of the southern Maya
D) all of the above