<ol>
<li>When Catherine the Great had a magnificent dinner service of Sevres porcelain made for her, she was scandalized by its great cost, (which became) the subject of prolonged controversy.</li>
</ol>
<p>(A) which became
(B) so it was to be
(C) with a result that it was destined to become
(D) therefore becoming
(E) consequently it would become</p>
<p>Why would D be wrong? Because of the cost of the porcelain, Catherine became the subject of controversy right? I don't think the sentence gives enough info to say whether the cost or Catherine is the subject of controversy.</p>