Which area likely provides the best farmland? Canadian Shield Great Plains Greenland Yucatán Peninsula

I am not completely sure, there may be different answers to this question:

Canadian Shield is not suitable for farmland, because it is very rocky.

Great Plains haven't been suitable in the past, because the land is very dry.

Greenland is covered in ice, although there are many places where farming is very successful.

Yucatan Peninsula is more or less a swamp today, but farming is possible.