Why are the Southern Colonies economy almost based completely on Farming?

Is the question written right or sould it be re worded.

I'd use the past tense -- "were."

... and an apostrophe to make "Colonies" plural possessive:

Colonies'

ok thanks for the help

Which one of the sentences below be correct if I'm talking about more than one of the southern colonies?

a)The southern colonie's economy was based on agriculture.
b)The southern colonies' economy was based on agriculture.

The question is written correctly but could be rephrased for clarity: "Why was the economy of the Southern Colonies primarily based on farming?"