GMAT Sentence Correction (SC) | Re: The Iroquois were primarily planters, but supplementing

More specifically,and is used as acoordinating conjunction in C, and so, must be followed with anIndependent clause (this is a property of coordinating conjunctions). In this case,and is just followed by adependent clause , and hence is not correct.

p.s. Sentence fragments are tested quite extensively on GMAT. Our book discusses in detail, the various scenarios in which Sentence fragments appear. If you could PM me your mail id, I can send you the relevant section.
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