GMAT Critical Reasoning (CR) | The Daisygen Company genetically engineers flowers which are

Option A is not an assumption. At most it could be a strengthening statement, though it would be better, if it said:

The genes that were spliced into the rose are not also responsible for causing the roses to have tearing effect, similar to that of onions.

(The genes that cause the onions to have tearing effect may not be carrying the same effect to roses.)

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