Four alternatives are given for the idiom/phrase in quotation marks in the sentence. Choose the alternative which best expresses the meaning of idiom/phrase.It is no longer easy to "strike gold" in Shakespeare's research since much work has already been done on him.

• A. Hit a golden spot
• B. Come across gold
• C. Come across the word "gold"
• D. Uncover or find a valuable line of argument or information