55.

Answer and Explanation

Your Answer is

Correct Answer is D

Explanation

According to the sentence meaning "Wyeth knows that this is the bold element needed in his paintings", so the attributive clause should be used here to modify the bold element, D is correct.

Item A/C: After the preposition, you can only add words but not sentences.

Item B: Where guides the attributive clause and the guide word (elements) should be the location, so it is wrong.