The correct answer is : The well-known artist arrived.
"well-known" is a compound modifier and, in the sentence above, is used immediately before the noun it modifies. For that reason, it must be hyphenated.
"chocolate-covered" could be hyphenated as well, but its location in the structure is improper for that use, since it comes after the noun it modifies.
Sedative is to anesthesiologist as capital is to a "D.corporation". This is primarily because sedatives are used by the former to achieve their goals and capital is used by the latter.
