The correct answer is
<span>B. (13) What have they accomplished so far
This sentence is a question that begs for the answer of what they have managed to do form the organization's founding up until now. That's why it needs to have a question mark at the end. It even has "what" which is one of the 5Ws of questions asking.</span>
This 200-year period saw unprecedented peace and economic prosperity throughout the Empire, which spanned from England in the north to Morocco in the south and Iraq in the east. During the Pax Romana, the Roman Empire reached its peak in terms of land area, and its population swelled to an estimated 70 million people.
A. is the sentence fragment.
