Here's the
official explanation provided by the GMAC for this question:
Option A: The sentence is meant to explain why farmers in earlier times began making cheese. However the underlined portion contains redundancy that makes it wordy, confusing, and unnecessarily awkward. The sentence would be much clearer if
this was how were omitted, given the later phrase
in this form, refers to the cheese form of dairy output.
Option B: Correct. This version contains none of the flaws noted above. Moreover, placing
in this form immediately following
could is a rhetorical improvement; it indicates more precisely that the possibility signaled by
could arose from the transformation of dairy output into cheese.
Option C: What
it refers to is quite unclear (for example, it makes no sense to say that making cheese was
a form of shipping). The phrase
form of shipping would reasonably be read as implying a contrast between modes of transport (for example road transport versus river transport), but this is inapplicable here.
Option D: This version tells us, in effect, that the output of dairy herds could be shipped to distant markets. But this fails to capture a crucial point of the explanation: that it was practical to ship dairy output to distant markets only in the form of cheese. In this context, the phrase
there was a way is wordy and unnecessarily awkward.
Option E: This version omits the notion of possibility signified by
could. The form
shipment … was done is awkward and offers no improvement on the verbal form
could be shipped.The wording also nonsensically suggests that cheese was a form in which shipment was done, rather than a form in which the output of dairy herds was shipped.
The correct answer is B.
Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.