I chose D but that is wrong. Is it ok to use has twice in a sentence, as in the OA?
The organic food industry has........that has convinced....!!
The structure of of the sentence is: The organic food industry has organized campaign
-............- that has convinced
The part between the two dashes is just modifier, so "that
" modifies "campaign
". Thus, the second "has" agrees with "campaign" not the main subject - the organic industry.
In addition, D is wrong because:
1. Verb tense. Past simple tense does not match with present perfect tense "has organized" because the effect of the action, organizing, is still effective at present. If you use "convinced", you mean the action is done, but it's not the intended meaning.
2. Too wordy. Clearly, "by using X, Y, and Z" is much better than "by the use of X, Y as well as Z".
Hope it helps.
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