The Iroquois were primarily planters, but supplementing their cultivation of maize, squash, and beans with fishing and hunting.
Error nalysis: 1) Subordinate clause "but supplementing..." does not have a proper verb and thus is a fragment.
2) Even if the auxiliary verb were used before "supplementing", it would remain incorrect because the sentence talks of an event that took place in the past. Thus, simple past "supplemented" is required to make the elements (simple past tense "were" in the main clause) in comparison equal.
Answer choice analysis
A) but supplementing : 1) This choice has the verb errors as pointed out in sentence analysis.
B) and had supplemented : 1) Conjunction "and" does not state the contrast between cultivation as the main source of food and hunting and fishing that just supplemented the main source.
2) The past perfect "had supplemented" is not required as there is no other event that is taking place in the past.
C) and even though they supplemented : 1) The conjunction "and" does not state the contrast between cultivation as the main source of food and hunting and fishing that just supplemented the main source.
2) "Even though" creates an expectation for something to follow. Absence of any such event makes the sentence incomplete.
D) although they supplemented : Correct. The conjunction 'but' clearly states the contrast between cultivation as the main source of food and hunting and fishing that just supplemented the main source. The simple past supplemented clearly states the meaning of the sentence.
E) but with supplementing: "But with" increases the ambiguity in the sentence by creating an expectation for something to follow.
2) "Supplementing" is not the finite verb for the second clause making it a fragment.
The OA is D.
