While in some cases an answer may be clearly better worded or more grammatically correct than all the others, in many other cases multiple answers may appear perfectly correct on their own. In such cases -- especially ones in which you are dealing with a large amount of underlined information -- you should take the extra time and double-check that your answer actually works in terms of syntax, clarity, and punctuation.
It is crucial that you pay attention to the punctuation aspect, particularly to the existing (non-underlined) commas within a sentence. This is because the comma splice (two full sentences joined only by a comma) is among the two or three most common types of wrong answer choices, and it shows up constantly. Constantly. If you're facing a full sentence on one side a comma, you can't have a full sentence on the other side. It doesn't matter how good it sounds or how much sense it makes in context -- it's always going to be wrong.
During the Renaissance, glass products made on the island of Murano could
only be crafted according to traditional techniques, whereby they forbade artisans
to leave and set up shop elsewhere.
(A) whereby they forbade artisans to leave
(B) as a result artisans were forbidden
(C) artisans were thus forbidden
(D) it being forbidden for artisans to leave
(E) and so artisans were forbidden
A and D are pretty clearly wrong, but B, C, and E all seem relatively plausible, right?
Here's the problem, though: the non-underlined portion of the sentence contains full sentence + comma, meaning that another full sentence *cannot* follow the comma without creating a comma splice.
If we plug these options into the sentence in turn, we get:
(B) During the Renaissance, glass products made on the island of Murano could